190 lines
6.8 KiB
Plaintext
190 lines
6.8 KiB
Plaintext
include ../_util-fns
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:marked
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# Once Upon a Time
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Every story starts somewhere. Our story starts where the [QuickStart](../quickstart.html) ends.
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:marked
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Follow the "QuickStart" steps. They provide the prerequisites, the folder structure,
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and the core files for our Tour of Heroes.
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<!--
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TODO: Recommend stagehand?
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-->
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Copy the "QuickStart" code to a new folder and rename the folder `angular2_tour_of_heroes`.
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We should have the following structure:
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.filetree
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.file angular2_tour_of_heroes
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.children
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.file lib
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.children
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.file app_component.dart
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.file web
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.children
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.file index.html
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.file main.dart
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.file pubspec.yaml
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// Add .file styles.css
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.p
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.callout.is-helpful
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header Source code
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:marked
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The complete source code for the example app in this chapter is
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[in GitHub](https://github.com/angular/angular.io/tree/master/public/docs/_examples/toh-1/dart).
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:marked
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## Keep the app compiling and running
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We want to start the Dart compiler, have it watch for changes, and start our server. We'll do this by typing
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code-example(format="" language="bash").
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pub serve
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:marked
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This command runs the compiler in watch mode, starts the server,
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and keeps the app running while we continue to build the Tour of Heroes.
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.l-main-section
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:marked
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## Show our Hero
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We want to display Hero data in our app.
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Let's add two properties to our `AppComponent`, a `title` property for the application name and a `hero` property
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for a hero named "Windstorm".
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+makeExample('toh-1/dart-snippets/app_component_snippets_pt1.dart', 'app-component-1', 'app_component.dart (AppComponent class)')(format=".")
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:marked
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Now we update the template in the `@Component` annotation with data bindings to these new properties.
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+makeExample('toh-1/dart-snippets/app_component_snippets_pt1.dart', 'show-hero')
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:marked
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The browser should refresh and display our title and hero.
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The double curly braces tell our app to read the `title` and `hero` properties from the component and render them.
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This is the "interpolation" form of one-way data binding.
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.l-sub-section
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:marked
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Learn more about interpolation in the [Displaying Data chapter](../guide/displaying-data.html).
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:marked
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### Hero object
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At the moment, our hero is just a name. Our hero needs more properties.
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Let's convert the `hero` from a literal string to a class.
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Create a `Hero` class with `id` and `name` properties.
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Keep this near the top of the `app_component.dart` file for now.
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+makeExample('toh-1/dart/lib/app_component.dart', 'hero-class-1', 'app_component.dart (Hero class)')(format=".")
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:marked
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Now that we have a `Hero` class, let’s refactor our component’s `hero` property to be of type `Hero`.
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Then initialize it with an id of `1` and the name, "Windstorm".
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+makeExample('toh-1/dart-snippets/app_component_snippets_pt1.dart', 'hero-property-1', 'app_component.dart (Hero property)')(format=".")
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:marked
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Because we changed the hero from a string to an object,
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we update the binding in the template to refer to the hero’s `name` property.
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+makeExample('toh-1/dart-snippets/app_component_snippets_pt1.dart', 'show-hero-2')
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:marked
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The browser refreshes and continues to display our hero’s name.
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### Adding more HTML
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Displaying a name is good, but we want to see all of our hero’s properties.
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We’ll add a `<div>` for our hero’s `id` property and another `<div>` for our hero’s `name`.
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+makeExample('toh-1/dart-snippets/app_component_snippets_pt1.dart', 'show-hero-properties')
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:marked
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Uh oh, our template string is getting long. We better take care of that to avoid the risk of making a typo in the template.
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### Multi-line template strings
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We could make a more readable template with string concatenation
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but that gets ugly fast, it is harder to read, and
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it is easy to make a spelling error. Instead,
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let’s take advantage of the template strings feature
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in Dart to maintain our sanity.
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Change the quotes around the template to triple quotes and
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put the `<h1>`, `<h2>` and `<div>` elements on their own lines.
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+makeExample('toh-1/dart-snippets/app_component_snippets_pt1.dart', 'multi-line-strings', 'app_component.dart (AppComponent\'s template)')(format=".")
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// omit back-tick warning
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.l-main-section
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:marked
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## Editing Our Hero
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We want to be able to edit the hero name in a textbox.
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Refactor the hero name `<label>` with `<label>` and `<input>` elements as shown below:
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+makeExample('toh-1/dart-snippets/app_component_snippets_pt1.dart', 'editing-Hero', 'app_component.dart (input element)')(format=".")
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:marked
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We see in the browser that the hero’s name does appear in the `<input>` textbox.
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But something doesn’t feel right.
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When we change the name, we notice that our change
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is not reflected in the `<h2>`. We won't get the desired behavior
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with a one-way binding to `<input>`.
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### Two-Way Binding
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We intend to display the name of the hero in the `<input>`, change it,
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and see those changes wherever we bind to the hero’s name.
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In short, we want two-way data binding.
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Let’s update the template to use the **`ngModel`** built-in directive for two-way binding.
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.l-sub-section
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:marked
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Learn more about `ngModel` in the
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[Forms](../guide/forms.html#ngModel) and
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[Template Syntax](../guide/template-syntax.html#ngModel) chapters.
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:marked
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Replace the `<input>` with the following HTML
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code-example(language="html").
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<input [(ngModel)]="hero.name" placeholder="name">
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:marked
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The browser refreshes. We see our hero again. We can edit the hero’s name and
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see the changes reflected immediately in the `<h2>`.
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.l-main-section
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:marked
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## The Road We’ve Travelled
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Let’s take stock of what we’ve built.
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* Our Tour of Heroes uses the double curly braces of interpolation (a form of one-way data binding)
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to display the application title and properties of a `Hero` object.
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* We wrote a multi-line template using Dart's template strings to make our template readable.
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* We can both display and change the hero’s name after adding a two-way data binding to the `<input>` element
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using the built-in `ngModel` directive.
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* The `ngModel` directive also propagates changes to every other binding of the `hero.name`.
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<!-- TODO:
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add [Run the live example for part 1](https://tour-of-heroes.firebaseapp.com/toh1/)
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-->
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Here's the complete `app_component.dart` as it stands now:
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+makeExample('toh-1/dart/lib/app_component.dart', 'pt1', 'app_component.dart')
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.l-main-section
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:marked
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## The Road Ahead
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Our Tour of Heroes only displays one hero and we really want to display a list of heroes.
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We also want to allow the user to select a hero and display their details.
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We’ll learn more about how to retrieve lists, bind them to the
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template, and allow a user to select it in the
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[next tutorial chapter](./toh-pt2.html).
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