angular-cn/public/docs/ts/latest/guide/upgrade.jade

include ../_util-fns

:marked
  Having an existing Angular 1 application doesn't mean that we can't
  begin enjoying everything Angular 2 has to offer. That's because Angular 2
  comes with built-in tools for migrating Angular 1 projects over to the
  Angular 2 platform.

  Some applications will be easier to upgrade than others, and there are
  ways in which we can make it easier for ourselves. It is possible to
  prepare and align Angular 1 applications with Angular 2 even before beginning
  the upgrade process. These preparation steps are all about making the code
  more decoupled, more maintainable, and up to speed with modern development
  tools. That means the preparation work will not only make the eventual upgrade
  easier, but will also generally improve our Angular 1 applications.

  One of the keys to a successful upgrade is to do it incrementally,
  by running the two frameworks side by side in the same application, and
  porting Angular 1 components to Angular 2 one by one. This makes it possible
  to upgrade even large and complex applications without disrupting other
  business, because the work can be done collaboratively and spread over
  a period of time. The `upgrade` module in Angular 2 has been designed to
  make incremental upgrading seamless.

  1. [Preparation](#preparation)
      1. [Following The Angular Style Guide](#following-the-angular-style-guide)
      2. [Using a Module Loader](#using-a-module-loader)
      3. [Migrating to TypeScript](#migrating-to-typescript)
      4. [Using Component Directives](#using-component-directives)
  2. [Upgrading with The Upgrade Adapter](#upgrading-with-the-upgrade-adapter)
      1. [How The Upgrade Adapter Works](#how-the-upgrade-adapter-works)
      2. [Bootstrapping Hybrid Angular 1+2 Applications](#bootstrapping-hybrid-angular-1-2-applications)
      3. [Using Angular 2 Components from Angular 1 Code](#using-angular-2-components-from-angular-1-code)
      4. [Using Angular 1 Component Directives from Angular 2 Code](#using-angular-1-component-directives-from-angular-2-code)
      5. [Projecting Angular 1 Content into Angular 2 Components](#projecting-angular-1-content-into-angular-2-components)
      6. [Transcluding Angular 2 Content into Angular 1 Component Directives](#transcluding-angular-2-content-into-angular-1-component-directives)
      7. [Making Angular 1 Dependencies Injectable to Angular 2](#making-angular-1-dependencies-injectable-to-angular-2)
      8. [Making Angular 2 Dependencies Injectable to Angular 1](#making-angular-2-dependencies-injectable-to-angular-1)
  3. [PhoneCat Upgrade Tutorial](#phonecat-upgrade-tutorial)
      1. [Switching to TypeScript](#switching-to-typescript)
      2. [Installing Angular 2](#installing-angular-2)
      3. [Bootstrapping A Hybrid 1+2 PhoneCat](#bootstrapping-a-hybrid-1-2-phonecat)
      4. [Upgrading the Phone service](#upgrading-the-phone-service)
      5. [Upgrading Components](#upgrading-components)
      6. [Switching To The Angular 2 Router And Bootstrap](#switching-to-the-angular-2-router-and-bootstrap)
      7. [Saying Goodbye to Angular 1](#saying-goodbye-to-angular-1)
  3. [Appendix: Upgrading PhoneCat Tests](#appendix-upgrading-phonecat-tests)

.l-main-section
:marked
  # Preparation

  There are many ways to structure Angular 1 applications. When we begin
  to upgrade these applications to Angular 2, some will turn out to be
  much more easy to work with than others. There are a few key techniques
  and patterns that we can apply to future proof our apps even before we
  begin the migration.

  ## Following The Angular Style Guide

  The [Angular 1 Style Guide](https://github.com/johnpapa/angular-styleguide/blob/master/a1/README.md#single-responsibility)
  collects patterns and practices that have been proven to result in
  cleaner and more maintainable Angular 1 applications. It contains a wealth
  of information about how to write and organize Angular code - and equally
  importantly - how **not** to write and organize Angular code.

  Angular 2 is a reimagined version of the best parts of Angular 1. In that
  sense, its goals are the same as the Angular Style Guide's: To preserve
  the good parts of Angular 1, and to avoid the bad parts. There's a lot
  more to Angular 2 than just that of course, but this does mean that
  *following the style guide helps make your Angular 1 app more closely
  aligned with Angular 2*.

  There are a few rules in particular that will make it much easier to do
  *an incremental upgrade* using the Angular 2 `upgrade` module:

  * The [Rule of 1](https://github.com/johnpapa/angular-styleguide/blob/master/a1/README.md#single-responsibility)
    states that there should be one component per file. This not only makes
    components easy to navigate and find, but will also allow us to migrate
    them between languages and frameworks one at a time. In this example application,
    each controller, component, service, and filter is in its own source file.
  * The [Folders-by-Feature Structure](https://github.com/johnpapa/angular-styleguide/blob/master/a1/README.md#folders-by-feature-structure)
    and [Modularity](https://github.com/johnpapa/angular-styleguide/blob/master/a1/README.md#modularity)
    rules define similar principles on a higher level of abstraction: Different parts of the
    application should reside in different directories and Angular modules.

  When an application is laid out feature per feature in this way, it can also be
  migrated one feature at a time. For applications that don't already look like
  this, applying the rules in the Angular style guide is a highly recommended
  preparation step. And this is not just for the sake of the upgrade - it is just
  solid advice in general!

  ## Using a Module Loader

  When we break application code down into one component per file, we often end
  up with a project structure with a large number of relatively small files. This is
  a much neater way to organize things than a small number of large files, but it
  doesn't work that well if you have to load all those files to the HTML page with
  `<script>` tags. Especially when you also have to maintain those tags in the correct
  order. That's why it's a good idea to start using a *module loader*.

  Using a module loader such as [SystemJS](https://github.com/systemjs/systemjs),
  [Webpack](http://webpack.github.io/), or [Browserify](http://browserify.org/)
  allows us to use the built-in module systems of the TypeScript or ES2015 languages in our apps.
  We can use the `import` and `export` features that explicitly specify what code can
  and will be shared between different parts of the application. For ES5 applications
  we can use CommonJS style `require` and `module.exports` features. In both cases,
  the module loader will then take care of loading all the code the application needs
  in the correct order.

  When we then take our applications into production, module loaders also make it easier
  to package them all up into production bundles with batteries included.

:marked
  ## Migrating to TypeScript

  If part of our Angular 2 upgrade plan is to also take TypeScript into use, it makes
  sense to bring in the TypeScript compiler even before the upgrade itself begins.
  This means there's one less thing to learn and think about during the actual upgrade.
  It also means we can start using TypeScript features in our Angular 1 code.

  Since TypeScript is a superset of ECMAScript 2015, which in turn is a superset
  of ECMAScript 5, "switching" to TypeScript doesn't necessarily require anything
  more than installing the TypeScript compiler and switching renaming files from
  `*.js` to `*.ts`. But just doing that is not hugely useful or exciting, of course.
  Additional steps like the following can give us much more bang for the buck:

  * For applications that use a module loader, TypeScript imports and exports
    (which are really ECMAScript 2015 imports and exports) can be used to organize
    code into modules.
  * Type annotations can be gradually added to existing functions and variables
    to pin down their types and get benefits like build-time error checking,
    great autocompletion support and inline documentation.
  * JavaScript features new to ES2015, like arrow functions, `let`s and `const`s,
    default function parameters, and destructuring assignments can also be gradually
    added to make the code more expressive.
  * Services and controllers can be turned into *classes*. That way they'll be a step
    closer to becoming Angular 2 service and component classes, which will make our
    life easier once we do the upgrade.

  ## Using Component Directives

  In Angular 2, components are the main primitive from which user interfaces
  are built. We define the different parts of our UIs as components, and then
  compose the UI by using components in our templates.

  You can also do this in Angular 1, using *component directives*. These are
  directives that define their own templates, controllers, and input/output bindings -
  the same things that Angular 2 components define. Applications built with
  component directives are much easier to migrate to Angular 2 than applications
  built with lower-level features like `ng-controller`,  `ng-include`, and scope
  inheritance.

  To be Angular 2 compatible, an Angular 1 component directive should configure
  these attributes:

  * `restrict: 'E'`. Components are usually used as elements.
  * `scope: {}` - an isolate scope. In Angular 2, components are always isolated
    from their surroundings, and we should do this in Angular 1 too.
  * `bindToController: {}`. Component inputs and outputs should be bound
    to the controller instead of using the `$scope`.
  * `controller` and `controllerAs`. Components have their own controllers.
  * `template` or `templateUrl`. Components have their own templates.

  Component directives may also use the following attributes:

  * `transclude: true`, if the component needs to transclude content from elsewhere.
  * `require`, if the component needs to communicate with some parent component's
    controller.

  Component directives **may not** use the following attributes:

  * `compile`. This will not be supported in Angular 2.
  * `replace: true`. Angular 2 never replaces a component element with the
    component template. This attribute is also deprecated in Angular 1.
  * `priority` and `terminal`. While Angular 1 components may use these,
    they are not used in Angular 2 and it is better not to write code
    that relies on them.

  An Angular 1 component directive that is fully aligned with the Angular 2
  architecture may look something like this:

+makeExample('upgrade-adapter/ts/app/hero-detail.directive.ts')

:marked
  Angular 1.5 introduces the [component API](https://docs.angularjs.org/api/ng/type/angular.Module)
  that makes it easier to define directives like these. It is a good idea to use
  this API for component directives for several reasons:

  * It requires less boilerplate code.
  * It enforces the use of component best practices like `controllerAs`.
  * It has good default values for directive attributes like `scope` and `restrict`.

  The component directive example from above looks like this when expressed
  using the component API:

+makeExample('upgrade-adapter/ts/app/upgrade-io/hero-detail.component.ts')

:marked
  Controller lifecycle hook methods `$onInit()`, `$onDestroy()`, and `$onChanges()`
  are another convenient feature that Angular 1.5 introduces. They all have nearly
  exact [equivalents in Angular 2](lifecycle-hooks.html), so organizing component lifecycle
  logic around them will ease the eventual Angular 2 upgrade process.

.l-main-section
:marked
  # Upgrading with The Upgrade Adapter

  The `upgrade` module in Angular 2 is a very useful tool for upgrading
  anything but the smallest of applications. With it we can mix and match
  Angular 1 and 2 components in the same application and have them interoperate
  seamlessly. That means we don't have to do the upgrade work all at once,
  since there's a natural coexistence between the two frameworks during the
  transition period.

  ## How The Upgrade Adapter Works

  The primary tool provided by the upgrade module is called the `UpgradeAdapter`.
  This is a service that can bootstrap and manage hybrid applications that support
  both Angular 2 and Angular 1 code.

  When we use `UpgradeAdapter`, what we're really doing is *running both versions
  of Angular at the same time*. All Angular 2 code is running in the Angular 2
  framework, and Angular 1 code in the Angular 1 framework. Both of these are the
  actual, fully featured versions of the frameworks. There is no emulation going on,
  so we can expect to have all the features and natural behavior of both frameworks.

  What happens on top of this is that components and services managed by one
  framework can interoperate with those from the other framework. This happens
  in three main areas: Dependency injection, the DOM, and change detection.

  ### Dependency Injection

  Dependency injection is front and center in both Angular 1 and
  Angular 2, but there are some key differences between the two
  frameworks in how it actually works.

table
  tr
    th Angular 1
    th Angular 2
  tr
    td
      :marked
        Dependency injection tokens are always strings
    td
      :marked
        Tokens [can have different types](../guide/dependency-injection.html).
        They are often classes. They may also be strings.
  tr
    td
      :marked
        There is exactly one injector. Even in multi-module applications,
        everything is poured into one big namespace.
    td
      :marked
        There is a [tree hierarchy of injectors](../guide/hierarchical-dependency-injection.html),
        with a root injector and an additional injector for each component.

:marked
  Even accounting for these differences we can still have dependency injection
  interoperability. The `UpgradeAdapter` resolves the differences and makes
  everything work seamlessly:

  * We can make Angular 1 services available for injection to Angular 2 code
    by *upgrading* them. The same singleton instance of each service is shared
    between the frameworks. In Angular 2 these services will always be in the
    *root injector* and available to all components. They will always have
    *string tokens* - the same tokens that they have in Angular 1.
  * We can also make Angular 2 services available for injection to Angular 1 code
    by *downgrading* them. Only services from the Angular 2 root injector can
    be downgraded. Again, the same singleton instances are shared between the frameworks.
    When we register a downgrade, we explicitly specify a *string token* that we want to
    use in Angular 1.

figure.image-display
  img(src="/resources/images/devguide/upgrade/injectors.png" alt="The two injectors in a hybrid application" width="700")

:marked
  ### Components and the DOM

  What we'll find in the DOM of a hybrid application are components and
  directives from both Angular 1 and Angular 2. These components
  communicate with each other by using the input and output bindings
  of their respective frameworks, which the `UpgradeAdapter` bridges
  together. They may also communicate through shared injected dependencies,
  as described above.

  There are two key things to understand about what happens in the DOM
  of a hybrid application:

  1. Every element in the DOM is owned by exactly one of the two
     frameworks. The other framework ignores it. If an element is
     owned by Angular 1, Angular 2 treats it as if it didn't exist,
     and vice versa.
  2. The root of the application *is always an Angular 1 template*.

  So a hybrid application begins life as an Angular 1 application,
  and it is Angular 1 that processes its root template. Angular 2 then steps
  into the picture when an Angular 2 component is used somewhere in
  the application templates. That component's view will then be managed
  by Angular 2, and it may use any number of Angular 2 components and
  directives.

  Beyond that, we may interleave the two frameworks as much as we need to.
  We always cross the boundary between the two frameworks by one of two
  ways:

  1. By using a component from the other framework: An Angular 1 template
     using an Angular 2 component, or an Angular 2 template using an
     Angular 1 component.
  2. By transcluding or projecting content from the other framework. The
    `UpgradeAdapter` bridges the related concepts of  Angular 1 transclusion
     and Angular 2 content projection together.

figure.image-display
 img(src="/resources/images/devguide/upgrade/dom.png" alt="DOM element ownership in a hybrid application" width="500")

:marked
  Whenever we use a component that belongs to the other framework, a
  switch between framework boundaries occurs. However, that switch only
  happens to the *children* of the component element. Consider a situation
  where we use an Angular 2 component from Angular 1 like this:

  ```
  <ng2-component></ng2-component>
  ```

  The DOM element `<ng2-component>` will remain to be an Angular 1 managed
  element, because it's defined in an Angular 1 template. That also
  means you can apply additional Angular 1 directives to it, but *not*
  Angular 2 directives. It is only in the template of the `Ng2Component`
  component where Angular 2 steps in. This same rule also applies when you
  use Angular 1 component directives from Angular 2.

:marked
  ### Change Detection

  Change detection in Angular 1 is all about `scope.$apply()`. After every
  event that occurs, `scope.$apply()` gets called. This is done either
  automatically by the framework, or in some cases manually by our own
  code. It is the point in time when change detection occurs and data
  bindings get updated.

  In Angular 2 things are different. While change detection still
  occurs after every event, no one needs to call `scope.$apply()` for
  that to happen. This is because all Angular 2 code runs inside something
  called the [Angular zone](../api/core/NgZone-class.html). Angular always
  knows when the code finishes, so it also knows when it should kick off
  change detection. The code itself doesn't have to call `scope.$apply()`
  or anything like it.

  In the case of hybrid applications, the `UpgradeAdapter` bridges the
  Angular 1 and Angular 2 approaches. Here's what happens:

  * Everything that happens in the application runs inside the Angular 2 zone.
    This is true whether the event originated in Angular 1 or Angular 2 code.
    The zone triggers Angular 2 change detection after every event.
  * The `UpgradeAdapter` will invoke the Angular 1 `$rootScope.$apply()` after
    every turn of the Angular zone. This also triggers Angular 1 change
    detection after every event.

figure.image-display
  img(src="/resources/images/devguide/upgrade/change_detection.png" alt="Change detection in a hybrid application" width="600")

:marked
  What this means in practice is that we do not need to call `$apply()` in
  our code, regardless of whether it is in Angular 1 on Angular 2. The
  `UpgradeAdapter` does it for us. We *can* still call `$apply()` so there
  is no need to remove such calls from existing code. Those calls just don't
  have any effect in a hybrid application.


:marked
  When we downgrade an Angular 2 component and then use it from Angular 1,
  the component's inputs will be watched using Angular 1 change detection.
  When those inputs change, the corresponding properties in the component
  are set. We can also hook into the changes by implementing the
  [OnChanges](../api/core/OnChanges-interface.html) interface in the component,
  just like we could if it hadn't been downgraded.

  Correspondingly, when we upgrade an Angular 1 component and use it from Angular 2,
  all the bindings defined for the component directive's `scope` (or `bindToController`)
  will be hooked into Angular 2 change detection. They will be treated
  as regular Angular 2 inputs and set onto the scope (or controller) when
  they change.

  ## Bootstrapping Hybrid Angular 1+2 Applications

  The first step to upgrading an application using the `UpgradeAdapter` is
  always to bootstrap it as a hybrid that supports both Angular 1 and
  Angular 2.

  Pure Angular 1 applications can be bootstrapped in two ways: By using an `ng-app`
  directive somewhere on the HTML page, or by calling
  [angular.bootstrap](https://docs.angularjs.org/api/ng/function/angular.bootstrap)
  from JavaScript. In Angular 2, only the second method is possible - there is
  no `ng-app` in Angular 2. This is also the case for hybrid applications.
  Therefore, it is a good preliminary step to switch Angular 1 applications to use the
  JavaScript bootstrap method even before switching them to hybrid mode.

  Say we have an `ng-app` driven bootstrap such as this one:

+makeExample('upgrade-adapter/ts/index-ng-app.html', null, null, {otl: /(ng-app.*ng-strict-di)/})

:marked
  We can remove the `ng-app` and `ng-strict-di` directives from the HTML
  and instead switch to calling `angular.bootstrap` from JavaScript, which
  will result in the same thing:

+makeExample('upgrade-adapter/ts/app/1-bootstrap/app.module.ts', 'bootstrap')

:marked
  To then switch the application into hybrid mode, we must first
  install Angular 2 to the project. Follow the instructions in
  [the QuickStart](../quickstart.html) for some pointers on this.
  When we have Angular 2 installed, we can import and instantiate
  the `UpgradeAdapter`, and then call its `bootstrap` method. It
  is designed to take the exact same arguments as
  [angular.bootstrap](https://docs.angularjs.org/api/ng/function/angular.bootstrap)
  so that it is easy to make the switch:

+makeExample('upgrade-adapter/ts/app/1-2-hybrid-bootstrap/app.module.ts', 'bootstrap')

:marked
  At this point we'll be running a hybrid Angular 1+2 application! All the
  existing Angular 1 code will work as it always did, but we are now ready
  to run Angular 2 code as well.

.alert.is-helpful
  :marked
    One notable difference between `angular.bootstrap` and
    `upgradeAdapter.bootstrap` is that the latter works *asynchronously*.
    This means that we cannot assume that the application has been instantiated
    immediately after the bootstrap call returns.

:marked
  As we begin to migrate components to Angular 2, we'll be using the
  `UpgradeAdapter` for more than just bootstrapping. It'll be important
  to use the **same** instance of the adapter across the whole application,
  because it stores internal information about what's going on in the application.
  It'll be useful to have a module for a shared `UpgradeAdapter` instance in
  the project:

+makeExample('upgrade-adapter/ts/app/1-2-hybrid-shared-adapter-bootstrap/upgrade_adapter.ts', null, 'upgrade_adapter.ts')

:marked
  This shared instance can then be pulled in to all the modules that need it:

+makeExample('upgrade-adapter/ts/app/1-2-hybrid-shared-adapter-bootstrap/app.module.ts', 'bootstrap')

:marked
  ## Using Angular 2 Components from Angular 1 Code
figure
  img(src="/resources/images/devguide/upgrade/a1-to-a2.png" alt="Using an Angular 2 component from Angular 1 code" align="left" style="width:250px; margin-left:-40px;margin-right:10px" )
:marked
  Once we're running a hybrid app, we can start the gradual process of upgrading
  code. One of the more common patterns for doing that is to use an Angular 2 component
  in an Angular 1 context. This could be a completely new component or one that was
  previously Angular 1 but has been rewritten for Angular 2.

  Say we have a simple Angular 2 component that shows information about a hero:

+makeExample('upgrade-adapter/ts/app/downgrade-static/hero-detail.component.ts', null, 'hero-detail.component.ts')

:marked
  If we want to use this component from Angular 1, we need to *downgrade* it
  using the upgrade adapter. What we get when we do that is an Angular 1
  *directive*, which we can then register into our Angular 1 module:

+makeExample('upgrade-adapter/ts/app/downgrade-static/app.module.ts', 'downgradecomponent')

:marked
  What we have here is an Angular 1 directive called `heroDetail`, which we can
  use like any other directive in our Angular 1 templates.

+makeExample('upgrade-adapter/ts/index-downgrade-static.html', 'usecomponent')

.alert.is-helpful
  :marked
    Note that since Angular 1 directives are matched based on their name,
    *the selector metadata of the Angular 2 component is not used in Angular 1*.
    It is matched as an element directive (`restrict: 'E'`) called `heroDetail`.

:marked
  Most components are not quite this simple, of course. Many of them
  have *inputs and outputs* that connect them to the outside world. An
  Angular 2 hero detail component with inputs and outputs might look
  like this:

+makeExample('upgrade-adapter/ts/app/downgrade-io/hero-detail.component.ts', null, 'hero-detail.component.ts')

:marked
  These inputs and outputs can be supplied from the Angular 1 template, and the
  `UpgradeAdapter` takes care of bridging them over:

+makeExample('upgrade-adapter/ts/index-downgrade-io.html', 'usecomponent')

:marked
  Note that even though we are in an Angular 1 template, **we're using Angular 2
  attribute syntax to bind the inputs and outputs**. This is a requirement for downgraded
  components. The expressions themselves are still regular Angular 1 expressions.

.callout.is-important
  header Use kebab-case for downgraded component attributes
  :marked
    There's one notable exception to the rule of using Angular 2 attribute syntax
    for downgraded components. It has to do with input or output names that consist
    of multiple words. In Angular 2 we would bind these attributes using camelCase:
  code-example(format="").
    [myHero]="hero"
  :marked
    But when using them from Angular 1 templates, we need to use kebab-case:
  code-example(format="").
    [my-hero]="hero"

:marked
  The `$event` variable can be used in outputs to gain access to the
  object that was emitted. In this case it will be the `Hero` object, because
  that is what was passed to `this.deleted.emit()`.

  Since this is an Angular 1 template, we can still use other Angular 1
  directives on the element, even though it has Angular 2 binding attributes on it.
  For  example, we can easily make multiple copies of the component using `ng-repeat`:

+makeExample('upgrade-adapter/ts/index-downgrade-io.html', 'userepeatedcomponent')

:marked
  ## Using Angular 1 Component Directives from Angular 2 Code
figure
  img(src="/resources/images/devguide/upgrade/a2-to-a1.png" alt="Using an Angular 1 component from Angular 2 code" align="left" style="width:250px; margin-left:-40px;margin-right:10px" )
:marked
  So, we can write an Angular 2 component and then use it from Angular 1
  code. This is very useful when we start our migration from lower-level
  components and work our way up. But in some cases it is more convenient
  to do things in the opposite order: To start with higher-level components
  and work our way down. This too can be done using the `UpgradeAdapter`.
  We can *upgrade* Angular 1 component directives and then use them from
  Angular 2.

  Not all kinds of Angular 1 directives can be upgraded. The directive
  really has to be a *component directive*, with the characteristics
  [described in the preparation guide above](#using-component-directives).
  Our safest bet for ensuring compatibility is using the
  [component API](https://docs.angularjs.org/api/ng/type/angular.Module)
  introduced in Angular 1.5.

  A simple example of an upgradable component is one that just has a template
  and a controller:

+makeExample('upgrade-adapter/ts/app/upgrade-static/hero-detail.component.ts', null, 'hero-detail.component.ts')

:marked
  We can *upgrade* this component to Angular 2 using the `UpgradeAdapter`'s
  `upgradeNg1Component` method. It takes the name of an Angular 1 component
  directive and returns an Angular 2 **component class**. When we then
  want to use it from an Angular 2 component, we list it the in the `directives`
  metadata of the component and then just use it in the Angular 2 template:

+makeExample('upgrade-adapter/ts/app/upgrade-static/container.component.ts', null, 'container.component.ts')

.alert.is-helpful
  :marked
    Upgraded components always have an element selector, which is based
    on the original name of the original Angular 1 component directive.

:marked
  An upgraded component may also have inputs and outputs, as defined by
  the scope/controller bindings of the original Angular 1 component
  directive. When we use the component from an Angular 2 template,
  we provide the inputs and outputs using **Angular 2 template syntax**,
  with the following rules:

table
  tr
    th
    th Binding definition
    th Template syntax
  tr
    th Attribute binding
    td
      :marked
        `myAttribute: '@myAttribute'`
    td
      :marked
        `<my-component myAttribute="value">`
  tr
    th Expression binding
    td
      :marked
        `myOutput: '&myOutput'`
    td
      :marked
        `<my-component (myOutput)="action()">`
  tr
    th Two-way binding
    td
      :marked
        `myValue: '=myValue'`
    td
      :marked
        As input: `<my-component [myValue]="anExpression">` or
        as two-way binding: `<my-component [(myValue)]="anExpression"`

:marked
  As an example, say we have a hero detail Angular 1 component directive
  with one input and one output:

+makeExample('upgrade-adapter/ts/app/upgrade-io/hero-detail.component.ts', null, 'hero-detail.component.ts')

:marked
  We can upgrade this component to Angular 2, and then provide the input
  and output using Angular 2 template syntax:

+makeExample('upgrade-adapter/ts/app/upgrade-io/container.component.ts', null, 'container.component.ts')


:marked
  ## Projecting Angular 1 Content into Angular 2 Components
figure
  img(src="/resources/images/devguide/upgrade/a1-to-a2-with-projection.png" alt="Projecting Angular 1 content into Angular 2" align="left" style="width:250px; margin-left:-40px;margin-right:10px" )
:marked
  When we are using a downgraded Angular 2 component from an Angular 1
  template, the need may arise to *transclude* some content into it. This
  is also possible. While there is no such thing as transclusion in Angular 2,
  there is a very similar concept called *content projection*. The `UpgradeAdapter`
  is able to make these two features interoperate.

  Angular 2 components that support content projection make use of an `<ng-content>`
  tag within them. Here's an example of such a component:

+makeExample('upgrade-adapter/ts/app/1-to-2-projection/hero-detail.component.ts', null, 'hero-detail.component.ts')

:marked
  When using the component from Angular 1, we can supply contents for it. Just
  like they would be transcluded in Angular 1, they get projected to the location
  of the `<ng-content>` tag in Angular 2:

+makeExample('upgrade-adapter/ts/index-1-to-2-projection.html', 'usecomponent')

.alert.is-helpful
  :marked
    When Angular 1 content gets projected inside an Angular 2 component, it still
    remains in "Angular 1 land" and is managed by the Angular 1 framework.

:marked
  ## Transcluding Angular 2 Content into Angular 1 Component Directives
figure
  img(src="/resources/images/devguide/upgrade/a2-to-a1-with-transclusion.png" alt="Projecting Angular 2 content into Angular 1" align="left" style="width:250px; margin-left:-40px;margin-right:10px" )
:marked
  Just like we can project Angular 1 content into Angular 2 components,
  we can *transclude* Angular 2 content into Angular 1 components, whenever
  we are using upgraded versions from them.

  When an Angular 1 component directive supports transclusion, it may use
  the `ng-transclude` directive in its template to mark the transclusion
  point:

+makeExample('upgrade-adapter/ts/app/2-to-1-transclusion/hero-detail.component.ts', null, 'hero-detail.component.ts')

.alert.is-helpful
  :marked
    The directive also needs to have the `transclude: true` option enabled.
    It is on by default for component directives defined with the
    1.5 component API.

:marked
  If we upgrade this component and use it from Angular 2, we can populate
  the component tag with contents that will then get transcluded:

+makeExample('upgrade-adapter/ts/app/2-to-1-transclusion/container.component.ts', null, 'container.component.ts')

:marked
  ## Making Angular 1 Dependencies Injectable to Angular 2

  When running a hybrid app, we may bump into situations where we need to have
  some Angular 1 dependencies to be injected to Angular 2 code. This may be
  because we have some business logic still in Angular 1 services, or because
  we need some of Angular 1's built-in services like `$location` or `$timeout`.

  In these situations, it is possible to *upgrade* an Angular 1 provider to
  Angular 2. This makes it possible to then inject it somewhere in Angular 2
  code. For example, we might have a service called `HeroesService` in Angular 1:

+makeExample('upgrade-adapter/ts/app/1-to-2-providers/heroes.service.ts', null, 'heroes.service.ts')

:marked
  We can upgrade the service using the `UpgradeAdapter`'s `upgradeNg1Provider` method
  by giving it the name of the service. This adds the service into Angular 2's root injector.

+makeExample('upgrade-adapter/ts/app/1-to-2-providers/app.module.ts', 'register', 'app.module.ts')

:marked
  We can then inject it in Angular 2 using a string token that matches
  its original name in Angular 1:

+makeExample('upgrade-adapter/ts/app/1-to-2-providers/hero-detail.component.ts', null, 'hero-detail.component.ts')

.alert.is-helpful
  :marked
    In this example we upgraded a service class, which has the added benefit that
    we can use a TypeScript type annotation when we inject it. While it doesn't
    affect how the dependency is handled, it enables the benefits of static type
    checking. This is not required though, and any Angular 1 service, factory, or
    provider can be upgraded.

:marked
  ## Making Angular 2 Dependencies Injectable to Angular 1

  In addition to upgrading Angular 1 dependencies, we can also *downgrade*
  Angular 2 dependencies, so that we can use them from Angular 1. This can be
  useful when we start migrating services to Angular 2 or creating new services
  in Angular 2 while we still have components written in Angular 1.

  For example, we might have an Angular 2 service called `Heroes`:

+makeExample('upgrade-adapter/ts/app/2-to-1-providers/heroes.ts', null, 'heroes.ts')

:marked
  We can again use the `UpgradeAdapter` for this, but first we need to register `Heroes`
  to the Angular 2 injector itself. In a pure Angular 2 application we would do this
  when we bootstrap the app, as described in the [dependency injection guide](dependency-injection.html#!#providers).
  But since hybrid applications are bootstrapped using the `UpgradeAdapter`, we also
  need to register our Angular 2 providers using `UpgradeAdapter`. It has a method
  called `addProvider` for this purpose.

  Once we've registered the Angular 2 provider, we can turn `Heroes` into an *Angular 1
  factory function* using `upgradeAdapter.downgradeNg2Provider()`. We can
  then plug the factory into an Angular 1 module, at which point we also choose what the
  name of the dependency will be in Angular 1:

+makeExample('upgrade-adapter/ts/app/2-to-1-providers/app.module.ts', 'register', 'app.module.ts')

:marked
  After this, the service is injectable anywhere in our Angular 1 code:

+makeExample('upgrade-adapter/ts/app/2-to-1-providers/hero-detail.component.ts', null, 'hero-detail.component.ts')





.l-main-section
:marked
  # PhoneCat Upgrade Tutorial

  In this section and we will look at a complete example of
  preparing and upgrading an application using the `upgrade` module. The app
  we're going to work on is [Angular PhoneCat](https://github.com/angular/angular-phonecat)
  from [the original Angular 1 tutorial](https://docs.angularjs.org/tutorial),
  which is where many of us began our Angular adventures. Now we'll see how to
  bring that application to the brave new world of Angular 2.

  During the process we'll learn how to apply the steps outlined in the
  [preparation guide](#preparation) in practice: We'll align the application
  with Angular 2 and also take TypeScript into use.

  To follow along with the tutorial, clone the
  [angular-phonecat](https://github.com/angular/angular-phonecat) repository
  and apply the steps as we go.

  In terms of project structure, this is where our work begins:

.filetree
  .file angular-phonecat
  .children
    .file bower.json
    .file karma.conf.js
    .file package.json
    .file app
    .children
      .file core
      .children
        .file checkmark
        .children
          .file checkmark.filter.js
          .file checkmark.filter.spec.js
        .file phone
        .children
          .file phone.module.js
          .file phone.service.js
          .file phone.service.spec.js
        .file core.module.js
      .file phone-detail
      .children
        .file phone-detail.component.js
        .file phone-detail.component.spec.js
        .file phone-detail.module.js
        .file phone-detail.template.html
      .file phone-list
      .children
        .file phone-list.component.js
        .file phone-list.component.spec.js
        .file phone-list.module.js
        .file phone-list.template.html
      .file img
      .children
        .file  ...
      .file phones
      .children
        .file  ...
      .file app.animations.js
      .file app.config.js
      .file app.css
      .file app.module.js
      .file index.html
    .file e2e-tests
    .children
      .file protractor-conf.js
      .file scenarios.js

:marked
  This is actually a pretty good starting point. The code uses the Angular 1.5
  component API and the organization follows the
  [Angular 1 Style Guide](https://github.com/johnpapa/angular-styleguide/blob/master/a1/README.md),
  which is an important [preparation step](#following-the-angular-style-guide) before
  a successful upgrade.

  * Each component, service, and filter is in its own source file, as per the
    [Rule of 1](https://github.com/johnpapa/angular-styleguide/blob/master/a1/README.md#single-responsibility).
  * The `core`, `phone-detail`, and `phone-list` modules are each in their
    own subdirectory. Those subdirectories contain the JavaScript code as well as
    the HTML templates that go with each particular feature. This is in line with the
    [Folders-by-Feature Structure](https://github.com/johnpapa/angular-styleguide/blob/master/a1/README.md#style-y152)
    and [Modularity](https://github.com/johnpapa/angular-styleguide/blob/master/a1/README.md#modularity)
    rules.
  * Unit tests are located side-by-side with application code where they are easily
    found, as described in the rules for
    [Organizing Tests](https://github.com/johnpapa/angular-styleguide/blob/master/a1/README.md#style-y197).

:marked
  ## Switching to TypeScript

  Since we're going to be writing our Angular 2 code in TypeScript, it makes sense to
  bring in the TypeScript compiler even before we begin upgrading.

  We will also start to gradually phase out the Bower package manager in favor
  of NPM. We'll install all new dependencies using NPM, and will eventually be
  able to remove Bower from the project.

  Let's begin by installing TypeScript to the project. While we're at it, let's also
  install the [Typings type definition manager](https://github.com/typings/typings).
  It will allow us to install type definitions for libraries that don't come with
  prepackaged types.

code-example(format="").
  npm i typescript typings --save-dev

:marked
  Let's also add run scripts for the `tsc` TypeScript compiler and the `typings`
  tool to `package.json`:

+makeJson('upgrade-phonecat-1-typescript/ts/package.json', {paths: 'scripts.tsc, scripts.tsc:w, scripts.typings'}, 'package.json')


:marked
  We can now use Typings to install type definitions for the existing libraries that
  we're using: Angular 1 and the Jasmine unit test framework.

code-example(format="").
  npm run typings install dt~jquery dt~angular dt~angular-route \
    dt~angular-resource dt~angular-mocks dt~angular-animate \
    dt~jasmine -- --save --global

:marked
  This will add these typings into a `typings.json` configuration file as well as
  download them into the `typings directory`.

  We should also configure the TypeScript compiler so that it can understand our
  project. We'll add a `tsconfig.json` file to the project directory, just like we do
  in the [Quickstart](../quickstart.html). It instructs the TypeScript compiler how
  to interpret our source files.

+makeJson('upgrade-phonecat-1-typescript/ts/tsconfig.ng1.json', null, 'tsconfig.json')

:marked
  We are telling the TypeScript compiler to turn our TypeScript files to ES5 code
  bundled into CommonJS modules.

  We can now launch the TypeScript compiler from the command line. It will watch
  our `.ts` source files and compile them to JavaScript on the fly. Those compiled
  `.js` files are then loaded into the browser by SystemJS. This is a process we'll
  want to have continuously running in the background as we go along.

code-example(format="").
  npm run tsc:w

:marked
  The next thing we'll do is convert our JavaScript files to TypeScript. Since
  TypeScript is a superset of ECMAScript 2015, which in turn is a superset
  of ECMAScript 5, we can simply switch the file extensions from `.js` to `.ts`
  and everything will work just like it did before. As the TypeScript compiler
  runs, it emits the corresponding `.js` file for every `.ts` file and the
  compiled JavaScript is what actually gets executed. If you start
  the project HTTP server with `npm start`, you should see the fully functional
  application in your browser.

  Now that we have TypeScript though, we can start benefiting from some of its
  features. There's a lot of value the language can provide to Angular 1 applications.

  For one thing, TypeScript is a superset of ES2015. Any app that has previously
  been written in ES5 - like the PhoneCat example has - can with TypeScript
  start incorporating all of the JavaScript features that are new to ES2015.
  These include things like `let`s and `const`s, arrow functions, default function
  parameters, and destructuring assignments.

  Another thing we can do is start adding *type safety* to our code. This has
  actually partially already happened because of the Angular 1 typings we installed.
  TypeScript are checking that we are calling Angular 1 APIs correctly when we do
  things like register components to Angular modules.

  But we can also start adding *type annotations* for our own code to get even more
  out of TypeScript's type system. For instance, we can annotate the checkmark
  filter so that it explicitly expects booleans as arguments. This makes it clearer
  what the filter is supposed to do.

+makeExample('upgrade-phonecat-1-typescript/ts/app/core/checkmark/checkmark.filter.ts', null, 'app/core/checkmark/checkmark.filter.ts')

:marked
  In the `Phone` service we can explicitly annotate the `$resource` service dependency
  as an `angular.resource.IResourceService` - a type defined by the Angular 1 typings.

+makeExample('upgrade-phonecat-1-typescript/ts/app/core/phone/phone.service.ts', null, 'app/core/phone/phone.service.ts')

:marked
  We can apply the same trick to the application's route configuration file in `app.config.ts`,
  where we are using the location and route services. By annotating them accordingly TypeScript
  can verify we're calling their APIs with the correct kinds of arguments.

+makeExample('upgrade-phonecat-1-typescript/ts/app/app.config.ts', null, 'app/app.config.ts')

.l-sub-section
  :marked
    The [Angular 1.x type definitions](https://github.com/DefinitelyTyped/DefinitelyTyped/tree/master/angularjs)
    we installed with Typings are not officially maintained by the Angular team,
    but are quite comprehensive. It is possible to make an Angular 1.x application
    fully type-annotated with the help of these definitions.

    If this is something we wanted to do, it would be a good idea to enable
    the `noImplicitAny` configuration option in `tsconfig.json`. This would
    cause the TypeScript compiler to display a warning when there's any code that
    does not yet have type annotations. We could use it as a guide to inform
    us about how close we are to having a fully annotated project.

:marked
  Another TypeScript feature we can make use of is *classes*. In particular, we
  can turn our component controllers into classes. That way they'll be a step
  closer to becoming Angular 2 component classes, which will make our life
  easier once we do the upgrade.

  Angular 1 expects controllers to be constructor functions. That's exactly what
  ES2015/TypeScript classes are under the hood, so that means we can just plug in a
  class as a component controller and Angular 1 will happily use it.

  Here's what our new class for the phone list component controller looks like:

+makeExample('upgrade-phonecat-1-typescript/ts/app/phone-list/phone-list.component.ts', null, 'app/phone-list/phone-list.component.ts')

:marked
  What was previously done in the controller function is now done in the class
  constructor function. The dependency injection annotations are attached
  to the class using a static property `$inject`. At runtime this becomes the
  `PhoneListController.$inject` property.

  The class additionally declares three members: The array of phones, the name of
  the current sort key, and the search query. These are all things we have already
  been attaching to the controller but that weren't explicitly declared anywhere.
  The last one of these isn't actually used in the TypeScript code since it's only
  referred to in the template, but for the sake of clarity we want to define all the
  members our controller will have.

  In the Phone detail controller we'll have two members: One for the phone
  that the user is looking at and another for the URL of the currently displayed image:

+makeExample('upgrade-phonecat-1-typescript/ts/app/phone-detail/phone-detail.component.ts', null, 'app/phone-detail/phone-detail.component.ts')

:marked
  This makes our controller code look a lot more like Angular 2 already. We're
  all set to actually introduce Angular 2 into the project.

  If we had any Angular 1 services in the project, those would also be
  a good candidate for converting to classes, since like controllers,
  they're also constructor functions. But we only have the `Phone` factory
  in this project, and that's a bit special since it's an `ngResource`
  factory. So we won't be doing anything to it in the preparation stage.
  We'll instead turn it directly into an Angular 2 service.

  ## Installing Angular 2

  Having completed our preparation work, let's get going with the Angular 2
  upgrade of PhoneCat. We'll do this incrementally with the help of the
  [upgrade module](#upgrading-with-the-upgrade-adapter) that comes with Angular 2.
  By the time we're done, we'll be able to remove Angular 1 from the project
  completely, but the key is to do this piece by piece without breaking the application.

.alert.is-important The project also contains some animations, which we are not yet upgrading in this version of the guide. This will change in a later release.

:marked
  Let's install Angular 2 into the project, along with the SystemJS module loader. Take a look into the
  [Quickstart](../quickstart.html) guide and get the following configurations from there:

  * Add Angular 2 and the other new dependencies to `package.json`
  * Add the new typings into `typings.json`
  * The SystemJS configuration file `systemjs.config.js` to the project root directory.

  Once these are done, run:

code-example(format="").
  npm install
  npm run typings install

:marked
  We can soon load Angular 2 dependencies into the application via `index.html`,
  but first we need to do some directory path adjustments. This is because we're going
  to need to load files from `node_modules` and the project root, whereas so far
  in this project everything has been loaded from the `/app` directory.

  Move the `app/index.html` file to the project root directory. Then change the
  development server root path in `package.json` to also point to the project root
  instead of `app`:

+makeJson('upgrade-phonecat-2-hybrid/ts/package.ng1.json', {paths: 'scripts.start'}, 'package.json')

:marked
  Now we're able to serve everything from the project root to the web browser. But we do *not*
  want to have to change all the image and data paths used in the application code to match
  our development setup. For that reason, we'll add a `<base>` tag to `index.html`, which will
  cause relative URLs to be resolved back to the `/app` directory:

+makeExample('upgrade-phonecat-2-hybrid/ts/index.html', 'base', 'index.html')

:marked
  Now we can load Angular 2 via SystemJS. We'll add the Angular 2 polyfills and the
  SystemJS config to the end of the `<head>` section, and then we'll use `System.import`
  to load the actual application:

+makeExample('upgrade-phonecat-2-hybrid/ts/index.html', 'ng2', 'index.html')

:marked
  In the `systemjs.config.js` file we got from the Quickstart we also need to make a couple
  of adjustments because of our project structure. We want to point the browser to the project
  root when loading things through SystemJS, instead of using the  `<base>` URL:

+makeExample('upgrade-phonecat-2-hybrid/ts/systemjs.config.1.js', 'paths', 'systemjs.config.js')

:marked
  ## Bootstrapping A Hybrid 1+2 PhoneCat

  What we'll do next is bootstrap the application as a *hybrid application*
  that supports both Angular 1 and Angular 2 components. Once we've done that
  we can start converting the individual pieces to Angular 2.

  To bootstrap a hybrid application, we first need to initialize an `UpgradeAdapter`,
  which [provides the glue](#upgrading-with-the-upgrade-adapter) that joins the two
  versions of the framework together. Let's import the `UpgradeAdapter` class into a
  new file `app/main.ts`. This file has been configured as the application entrypoint
  in `systemjs.config.js`, so it is already being loaded by the browser.

+makeExample('upgrade-phonecat-2-hybrid/ts/app/main.ts', 'import-adapter', 'app/main.ts')

:marked
  We can then make an adapter by instantiating the class:

+makeExample('upgrade-phonecat-2-hybrid/ts/app/main.ts', 'init-adapter')

:marked
  Our application is currently bootstrapped using the Angular 1 `ng-app` directive
  attached to the `<html>` element of the host page. This will no longer work with
  Angular 2. We should switch to a JavaScript-driven bootstrap instead. So, remove the
  `ng-app` attribute from `index.html`, and instead add this to `main.ts`:

+makeExample('upgrade-phonecat-2-hybrid/ts/app/main.ts', 'bootstrap')

:marked
  The arguments used here are the root element of the application (which is
  the same element we had `ng-app` on earlier), and the Angular 1.x modules
  that we want to load. Since we're bootstrapping the app through
  an `UpgradeAdapter`, we're actually now running the app as a hybrid Angular 1+2
  app.

  This means we are now running both Angular 1 and 2 at the same time. That's pretty
  exciting! We're not running any actual Angular 2 components yet though,
  so let's do that next.


:marked
  ## Upgrading the Phone service

  The first piece we'll port over to Angular 2 is the `Phone` service, which
  resides in `app/core/phone/phone.service.ts` and makes it possible for components
  to load phone information from the server. Right now it's implemented with
  ngResource and we're using it for two things:

  * For loading the list of all phones into the phone list component
  * For loading the details of a single phone into the phone detail component.

  We can replace this implementation with an Angular 2 service class, while
  keeping our controllers in Angular 1 land. In the new version we'll just use
  the `Http` service from Angular 2 instead of ngResource.

  Before the `Http` service is available for injection, we need to register
  it into our application's dependency injector. We should import the `HTTP_PROVIDERS`
  constant in `main.ts`:

+makeExample('upgrade-phonecat-2-hybrid/ts/app/main.ts', 'import-http')

:marked
  In a regular Angular 2 application we would now pass `HTTP_PROVIDERS` into
  the application bootstrap function. But we can't do that in a hybrid
  application such as the one we're working on. That's because the `bootstrap`
  method of  `UpgradeAdapter` expects Angular 1 modules as dependencies,
  not Angular 2 providers.

  What we must do instead is register `HTTP_PROVIDERS` into the `UpgradeAdapter`
  separately. It has a method called `addProvider` for that purpose:

+makeExample('upgrade-phonecat-2-hybrid/ts/app/main.ts', 'add-http')

:marked
  Now we're ready to upgrade the Phone service itself. We replace the ngResource-based
  service in `phone.service.ts` with a TypeScript class decorated as `@Injectable`:

+makeExample('upgrade-phonecat-2-hybrid/ts/app/core/phone/phone.service.ts', 'classdef', 'app/core/phone/phone.service.ts')

:marked
  The `@Injectable` decorator will attach some dependency injection metadata
  to the class, letting Angular 2 know about its dependencies. As described
  by our [Dependency Injection Guide](../guide/dependency-injection.html),
  this is a marker decorator we need to use for classes that have no other
  Angular 2 decorators but still need to have their dependencies injected.

  In its constructor the class expects to get the `Http` service. It will
  be injected to it and it is stored as a private field. The service is then
  used in the two instance methods, one of which loads the list of all phones,
  and the other the details of a particular phone:

+makeExample('upgrade-phonecat-2-hybrid/ts/app/core/phone/phone.service.ts', 'fullclass')

:marked
  The methods now return Observables of type `PhoneData` and `PhoneData[]`. This is
  a type we don't have yet, so let's add a simple interface for it:

+makeExample('upgrade-phonecat-2-hybrid/ts/app/core/phone/phone.service.ts', 'phonedata-interface', 'app/core/phone/phone.service.ts')

:marked
  Here's the full, final code for the service:

+makeExample('upgrade-phonecat-2-hybrid/ts/app/core/phone/phone.service.ts', null, 'app/core/phone/phone.service.ts')

:marked
  Notice that we're importing the `map` operator of the RxJS `Observable` separately.
  We need to do this for all RxJS operators that we want to use, since Angular 2
  does not load all of them by default.

  The new `Phone` service now has the same features that the original, ngResource based
  service did. Now we just need to register the new service into the application, so that
  our Angular 1 components will be able to use it.

  `UpgradeAdapter` has a `downgradeNg2Provider` method for the purpose of making
  Angular 2 services available to Angular 1 code. We can use it to plug in our
  `Phone` service:

+makeExample('upgrade-phonecat-2-hybrid/ts/app/main.ts', 'phone-service', 'app/main.ts')

:marked
  Note that we actually needed to do two registrations here:

  1. Register `Phone` as an **Angular 2 provider** with the `addProvider`
     method. That's the same method that we used earlier for `HTTP_PROVIDERS`.
  2. Register an **Angular 1 factory** called `phone`, which will be a *downgraded*
     version of the `Phone` Angular 2 service.

  Now that we are loading `phone.service.ts` through an import that is resolved
  by SystemJS, we should **remove the `<script>` tag** for the service from `index.html`.
  This is something we'll do to all our components as we upgrade them. Simultaneously
  with the Angular 1 to 2 upgrade we're also migrating our code from scripts to modules.

  At this point we can switch our two components to use the new service
  instead of the old one. We `$inject` it as the downgraded `phone` factory,
  but it's really an instance of the `Phone` class and we can annotate its type
  accordingly:

+makeExample('upgrade-phonecat-2-hybrid/ts/app/phone-list/phone-list.component.ng1.ts', null, 'app/phone-list/phone-list.component.ts')

+makeExample('upgrade-phonecat-2-hybrid/ts/app/phone-detail/phone-detail.component.ng1.ts', null, 'app/phone-detail/phone-detail.component.ts')


:marked
  What we have here are two Angular 1 components using an Angular 2 service!
  The components don't need to be aware of this, though the fact that the
  service returns Observables and not Promises is a bit of a giveaway.
  In any case, what we've achieved is a migration of a service to Angular 2
  without having to yet migrate the components that use it.

.alert.is-helpful
  :marked
    We could also use the `toPromise` method of `Observable` to turn those
    Observables into Promises in the service. This can in many cases further
    reduce the amount of changes needed in the component controllers.

:marked
  ## Upgrading Components

  Next, let's upgrade our Angular 1 components to Angular 2 components. We'll
  do it one at a time, while still keeping the application in hybrid mode.
  As we make these conversions, we'll also be defining our first Angular 2 *pipes*.

  Let's look at the phone list component first. Right now it contains a TypeScript
  controller class and a component definition object. We can morph this into
  an Angular 2 component by just renaming the controller class and turning the
  Angular 1 component definition object into an Angular 2 `@Component` decorator.
  We can then also remove the static `$inject` property from the class:

+makeExample('upgrade-phonecat-2-hybrid/ts/app/phone-list/phone-list.component.ts', 'initialclass', 'app/phone-list/phone-list.component.ts')

:marked
  The `selector` attribute is a CSS selector that defines where on the page the component
  should go. In Angular 1 we do matching based on component names, but in Angular 2 we
  have these explicit selectors. This one will match elements with the name `phone-list`,
  just like the Angular 1 version did.

  We now also need to convert the template of this component into Angular 2 syntax.
  In the search controls we need to use Angular 2 syntax for the two `ngModel`s.
  We should also no longer use the `$ctrl` prefix in expressions:

+makeExample('upgrade-phonecat-2-hybrid/ts/app/phone-list/phone-list.template.html', 'controls', 'app/phone-list/phone-list.template.html')

:marked
  In the list we need to replace the `ng-repeat` with an `*ngFor` and the
  `let var of iterable` syntax, which is [described in our
  Template Syntax guide](../guide/template-syntax.html#directives).
  For the images, we can replace `ng-src` with a binding to the standard `src` property.

+makeExample('upgrade-phonecat-2-hybrid/ts/app/phone-list/phone-list.template.html', 'list', 'app/phone-list/phone-list.template.html')

:marked
  Another thing that we've done here is that we've removed the use of `filter` and `orderBy` filters,
  and replaced them with a call to the `getPhones()` controller method.
  The built-in Angular filters `filter` and `orderBy` do not exist in Angular 2,
  so we need to do the filtering and sorting ourselves. We could define our own Angular 2
  pipes for this purpose, but in this case it is more convenient to just implement the filtering
  and ordering logic in the component itself. We expect the `getPhones()` method to return a collection
  where the current filtering and ordering has been applied.

+makeExample('upgrade-phonecat-2-hybrid/ts/app/phone-list/phone-list.component.ts', 'getphones', 'app/phone-list/phone-list.component.ts')

:marked
  In the entrypoint file `main.ts` we're going to plug this component into our application. Instead
  of registering a component, we register a `phoneList` *directive*.
  The directive is a downgraded version of our Angular 2 component, and the `UpgradeAdapter`
  handles the bridging between the two:

+makeExample('upgrade-phonecat-2-hybrid/ts/app/main.ts', 'phone-list', 'app/main.ts')

:marked
  The `<angular.IDirectiveFactory>` type annotation here is to let the TypeScript compiler
  know that the return value of the downgrade method call will be something that can be
  used as a directive factory.

  At this point, also remove the `<script>` tag for the phone list component from `index.html`.

  Now we can start looking at our other component, which is the one for
  the phone details. Set the contents of `phone-detail.component.ts` as follows:

+makeExample('upgrade-phonecat-2-hybrid/ts/app/phone-detail/phone-detail.component.ts', 'initialclass', 'app/phone-detail/phone-detail.component.ts')

:marked
  This is pretty similar to what we did with the phone list. The one new change
  here is the use of `@Inject` for the `$routeParams` dependency. It tells the
  Angular 2 injector what this dependency should map to. We have a dependency called
  `$routeParams` in the Angular 1 injector, where it is provided by the Angular 1 router.
  That is what we were already using when `PhoneDetails` was still an Angular 1 controller.

  The things is though, Angular 1 dependencies are not made automatically available to
  Angular 2 components, so if we were to run this now, it would not work. We need to explicitly
  tell the `UpgradeAdapter` to upgrade `$routeParams` so that it is available for injection in
  Angular 2. We can do it in `main.ts`:

+makeExample('upgrade-phonecat-2-hybrid/ts/app/main.ts', 'routeparams', 'app/main.ts')



:marked
  We now also need to convert the template of this component into Angular 2 syntax.
  Here is the new template in its entirety:

+makeExample('upgrade-phonecat-2-hybrid/ts/app/phone-detail/phone-detail.template.html', null, 'app/phone-detail/phone-detail.template.html')

:marked
  There are several notable changes here:

  * We've removed the `$ctrl.` prefix from all expressions.
  * Just like we did in the phone list, we've replaced `ng-src` with property
    bindings for the standard `src` property.
  * We're using the property binding syntax around `ng-class`. Though Angular 2
    does have [a very similar `ngClass`](../guide/template-syntax.html#directives)
    as Angular 1 does, its value is not magically evaluated as an expression.
    In Angular 2 we always specify  in the template when an attribute's value is
    a property expression, as opposed to a literal string.
  * We've replaced `ng-repeat`s with `*ngFor`s.
  * We've replaced `ng-click` with an event binding for the standard `click`.
  * We've wrapped the whole template in an `ngIf` that causes it only to be
    rendered when there is a phone present. We need this because when the component
    first loads, we don't have `phone` yet and the expressions will refer to a
    non-existing value. Unlike in Angular 1, Angular 2 expressions do not fail silently
    when we try to refer to properties on undefined objects. We need to be explicit
    about cases where this is expected.

:marked
  In `main.ts` we'll now register a `phoneDetail` directive instead of a
  component. The directive is a downgraded version of the `PhoneDetail` Angular 2
  component.

+makeExample('upgrade-phonecat-2-hybrid/ts/app/main.ts', 'phone-detail', 'app/main.ts')

:marked
  We should now also remove the phone detail component `<script>` tag from `index.html`.

  There's one additional step we need to take, which is to upgrade the
  `checkmark` filter that the template is using. We need an Angular 2
  pipe instead of an Angular 1 filter.

  While there is no upgrade method in the upgrade adapter for filters, we
  can just turn the filter function into a class that fulfills
  the contract for Angular 2 Pipes. The implementation is the same as before.
  It just comes in a different kind of packaging. While changing it, also
  rename the file to `checkmark.pipe.ts`:

+makeExample('upgrade-phonecat-2-hybrid/ts/app/core/checkmark/checkmark.pipe.ts', null, 'app/core/checkmark/checkmark.pipe.ts')

:marked
  In the component we should now import and declare our newly created pipe (as well as
  remove the filter `<script>` tag from `index.html`):

+makeExample('upgrade-phonecat-2-hybrid/ts/app/phone-detail/phone-detail.component.ts', 'checkmark-pipe', 'app/phone-detail/phone-detail.component.ts')

:marked
  ## Switching To The Angular 2 Router And Bootstrap

  At this point we've replaced all our Angular 1 application components with
  their Angular 2 counterparts. The application is still bootstrapped as a hybrid,
  but there isn't really any need for that anymore, and we can begin to
  pull out the last remnants of Angular 1.

  There are just two more things to do: We need to switch the router to
  the Angular 2 one, and then bootstrap the app as a pure Angular 2 app.

  Let's do the routing part first. Angular 2 comes with an [all-new router](router.html)
  that we can use for this.

  Angular 2 applications all have a *root component*, which, among other
  things, is where we should plug in the router. We don't yet have such a root
  component, because our app is still managed as an Angular 1 app.
  Let's change this now and add an `AppComponent` class into a new file
  `app.component.ts`:

+makeExample('upgrade-phonecat-3-final/ts/app/app.component.ts', null, 'app/app.component.ts')

:marked
  This is a component that plugs in to an `<phonecat-app>` element on the page,
  and has a simple template that only includes the router outlet component
  of the Angular router. This means that the component just renders the contents
  of the current route and nothing else. The `@RouteConfig` decorator defines
  the Angular 2 counterparts of our two routes. They refer directly to the
  two components.

  We should put this `<phonecat-app>` element in the HTML so that the root component
  has something to attach to. It replaces the old Angular 1 `ng-view` directive:

+makeExample('upgrade-phonecat-3-final/ts/index.html', 'appcomponent', 'index.html')

:marked
  In the `PhoneDetail` component we now need to change how the phone id parameter
  is received. There will be no more `$routeParams` injection available, because
  that comes from the Angular 1 router. Instead, what we have is a `RouteParams`
  object provided by the Angular 2 router. We use it to obtain the `phoneId` from
  the params:

+makeExample('upgrade-phonecat-3-final/ts/app/phone-detail/phone-detail.component.ts', null, 'app/phone-detail/phone-detail.component.ts')

:marked
  With that, we're ready to switch the bootstrap method of the application from that
  of the `UpgradeAdapter` to the main Angular 2 `bootstrap`. Let's import it together
  with the router, the new app component, and everything else in `main.ts`

+makeExample('upgrade-phonecat-3-final/ts/app/main.ts', 'imports')

:marked
  We'll now use the regular Angular 2 `bootstrap` function to bootstrap the app
  instead of using `UpgradeAdapter`. The first argument to `bootstrap` is the
  application's root component `AppComponent`, and the second
  is an array of the Angular 2 providers that we want to make available for
  injection. In that array we include all the things we have been registering
  with  `upgradeAdapter.addProvider` until now, as well as the providers and
  directives of the router:

+makeExample('upgrade-phonecat-3-final/ts/app/main.ts', 'bootstrap')

:marked
  We also configure a couple of things for the router here so that the application
  URL paths match exactly those we had in the Angular 1 app: We want the
  hash location strategy with the `!` prefix: `#!/phones`.

  At this point we are running a pure Angular 2 application!

  But there's actually one more cool thing we can do with the new router.
  We no longer have to hardcode the links to phone details from the phone
  list, because the Angular 2 router is able to generate them for us with
  its `routerLink` directive. We just need to refer to the route names we
  used in the `@RouteConfig`:

+makeExample('upgrade-phonecat-3-final/ts/app/phone-list/phone-list.template.html', 'list', 'app/phone-list/phone-list.template.html')

:marked
  For this to work the directive just needs to be declared in the component:

+makeExample('upgrade-phonecat-3-final/ts/app/phone-list/phone-list.component.ts', 'top')

:marked
  ## Saying Goodbye to Angular 1

  It is time to take off the training wheels and let our application begin
  its new life as a pure, shiny Angular 2 app. The remaining tasks all have to
  do with removing code - which of course is every programmer's favorite task!

  If you haven't already, remove all references to the `UpgradeAdapter` from `main.ts`.
  Also remove the Angular 1 bootstrap code.

  When you're done, this is what `main.ts` should look like:

+makeExample('upgrade-phonecat-3-final/ts/app/main.ts', null, 'app/main.ts')

:marked
  You may also completely remove the following files. They are Angular 1
  module configuration files and not needed in Angular 2:

  * `app/app.module.ts`
  * `app/app.config.ts`
  * `app/core/core.module.ts`
  * `app/core/phone/phone.module.ts`
  * `app/phone-detail/phone-detail.module.ts`
  * `app/phone-list/phone-list.module.ts`

  The external typings for Angular 1 may be uninstalled as well. The only ones
  we still need are for Jasmine and Angular 2 polyfills.

code-example(format="").
  npm run typings uninstall jquery -- --save --global
  npm run typings uninstall angular -- --save --global
  npm run typings uninstall angular-route -- --save --global
  npm run typings uninstall angular-resource -- --save --global
  npm run typings uninstall angular-mocks -- --save --global
  npm run typings uninstall angular-animate -- --save --global

:marked
  Finally, from `index.html`, remove all references to
  Angular 1 scripts, the Angular 2 upgrade module, and jQuery. When we're done,
  this is what it should look like:

+makeExample('upgrade-phonecat-3-final/ts/index.html', 'full', 'index.html')

:marked
  That is the last we'll see of Angular 1! It has served us well but now
  it's time to say goodbye.



.l-main-section
:marked
  # Appendix: Upgrading PhoneCat Tests

  Tests can not only be retained through an upgrade process, but they can also be
  used as a valuable safety measure when ensuring that the application does not
  break during the upgrade. E2E tests are especially useful for this purpose.

  ## E2E Tests

  The PhoneCat project has both E2E Protractor tests and some Karma unit tests in it.
  Of these two, E2E tests can be dealt with much more easily: By definition,
  E2E tests access our application from the *outside* by interacting with
  the various UI elements the app puts on the screen. E2E tests aren't really that
  concerned with the internal structure of the application components. That
  also means that although we modify our project quite a bit during the upgrade, the E2E
  test suite should keep passing with just minor modifications. This is because
  we don't change how the application behaves from the user's point of view.

  During TypeScript conversion, there is nothing we have to do to keep E2E tests
  working. It is only when we start to upgrade components and their template to Angular 2
  that we need to make some changes. This is because the E2E tests have matchers
  that are specific to Angular 1. For PhoneCat we need to make the following changes
  in order to make things work with Angular 2:

table
  tr
    th Previous code
    th New code
    th Notes
  tr
    td
      :marked
        `by.repeater('phone in $ctrl.phones').column('phone.name')`
    td
      :marked
        `by.css('.phones .name')`
    td
      :marked
        The repeater matcher relies on Angular 1 `ng-repeat`
  tr
    td
      :marked
        `by.repeater('phone in $ctrl.phones')`
    td
      :marked
        `by.css('.phones li')`
    td
      :marked
        The repeater matcher relies on Angular 1 `ng-repeat`
  tr
    td
      :marked
        `by.model('$ctrl.query')`
    td
      :marked
        `by.css('input')`
    td
      :marked
        The model matcher relies on Angular 1 `ng-model`
  tr
    td
      :marked
        `by.model('$ctrl.orderProp')`
    td
      :marked
        `by.css('select')`
    td
      :marked
        The model matcher relies on Angular 1 `ng-model`
  tr
    td
      :marked
        `by.binding('$ctrl.phone.name')`
    td
      :marked
        `by.css('h1')`
    td
      :marked
        The binding matcher relies on Angular 1 data binding


:marked
  When the bootstrap method is switched from that of `UpgradeAdapter` to
  pure Angular 2, Angular 1 ceases to exist on the page completely.
  At this point we need to tell Protractor that it should not be looking for
  an Angular 1 app anymore, but instead it should find *Angular 2 apps* from
  the page. The following change is then needed in `protractor-conf.js`:

code-example(format="").
  useAllAngular2AppRoots: true,

:marked
  Also, there are a couple of Protractor API calls in the PhoneCat test code that
  are using the Angular 1 `$location` service under the hood. As that
  service is no longer there after the upgrade, we need to replace those calls with ones
  that use WebDriver's generic URL APIs instead. The first of these is
  the redirection spec:

+makeExample('upgrade-phonecat-3-final/e2e-spec.js', 'redirect', 'e2e-tests/scenarios.js')

:marked
  And the second is the phone links spec:

+makeExample('upgrade-phonecat-3-final/e2e-spec.js', 'links', 'e2e-tests/scenarios.js')



:marked
  ## Unit Tests

  For unit tests, on the other hand, more conversion work is needed. Effectively
  they need to be *upgraded* along with the production code.

  During TypeScript conversion no changes are strictly necessary. But it may be
  a good idea to convert the unit test code into TypeScript as well, as the same
  benefits we from TypeScript in production code also applies to tests.

  For instance, in the phone detail component spec we can use not only ES2015
  features like arrow functions and block-scoped variables, but also type
  definitions for some of the Angular 1 services we're consuming:

+makeExample('upgrade-phonecat-1-typescript/ts/app/phone-detail/phone-detail.component.spec.ts', null, 'app/phone-detail/phone-detail.component.spec.ts')

:marked
  Once we start the upgrade process and bring in SystemJS, configuration changes
  are needed for Karma. We need to let SystemJS load all the new Angular 2 code,
  which can be done with the following kind of shim file:

+makeExample('upgrade-phonecat-2-hybrid/ts/karma-test-shim.1.js', null, 'karma-test-shim.js')

:marked
  The shim first loads the SystemJS configuration, then Angular 2's test support libraries,
  and then the application's spec files themselves.

  Karma configuration should then be changed so that it uses the application root dir
  as the base directory, instead of `app`.

+makeExample('upgrade-phonecat-2-hybrid/ts/karma.conf.ng1.js', 'basepath', 'karma.conf.js')

:marked
  Once this is done, we can load SystemJS and other dependencies, and also switch the configuration
  for loading application files so that they are *not* included to the page by Karma. We'll let
  the shim and SystemJS load them.

+makeExample('upgrade-phonecat-2-hybrid/ts/karma.conf.ng1.js', 'files', 'karma.conf.js')

:marked
  Since the HTML templates of Angular 2 components will be loaded as well, we need to help
  Karma out a bit so that it can route them to the right paths:

+makeExample('upgrade-phonecat-2-hybrid/ts/karma.conf.ng1.js', 'html', 'karma.conf.js')

:marked
  The unit test files themselves also need to be switched to Angular 2 when their production
  counterparts are switched. The specs for the checkmark pipe are probably the most straightforward,
  as the pipe has no dependencies:

+makeExample('upgrade-phonecat-2-hybrid/ts/app/core/checkmark/checkmark.pipe.spec.ts', null, 'app/core/checkmark/checkmark.pipe.spec.ts')

:marked
  The unit test for the phone service is a bit more involved. We need to switch from the mocked-out
  Angular 1 `$httpBackend` to a mocked-out Angular 2 Http backend.

+makeExample('upgrade-phonecat-2-hybrid/ts/app/core/phone/phone.service.spec.ts', null, 'app/core/phone/phone.service.spec.ts')

:marked
  For the component specs we can mock out the `Phone` service itself, and have it provide
  canned phone data. We use Angular's component unit testing APIs for both components.

+makeExample('upgrade-phonecat-2-hybrid/ts/app/phone-detail/phone-detail.component.spec.ts', null, 'app/phone-detail/phone-detail.component.spec.ts')

+makeExample('upgrade-phonecat-2-hybrid/ts/app/phone-list/phone-list.component.spec.ts', null, 'app/phone-list/phone-list.component.spec.ts')


:marked
  Finally, we need to revisit both of the component tests when we switch to the Angular 2
  router. For the details component we need to provide an Angular 2 `RouteParams` object
  instead of using the Angular 1 `$routeParams`.

+makeExample('upgrade-phonecat-3-final/ts/app/phone-detail/phone-detail.component.spec.ts', 'routeparams', 'app/phone-detail/phone-detail.component.spec.ts')

:marked
  And for the phone list component we need to set up a few things for the router itself so that
  the route link directive will work.

+makeExample('upgrade-phonecat-3-final/ts/app/phone-list/phone-list.component.spec.ts', 'routestuff', 'app/phone-list/phone-list.component.spec.ts')