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