250 lines
9.4 KiB
Markdown
250 lines
9.4 KiB
Markdown
# The Hero Editor
|
|
|
|
The application now has a basic title.
|
|
Next you will create a new component to display hero information
|
|
and place that component in the application shell.
|
|
|
|
## Create the heroes component
|
|
|
|
Using the Angular CLI, generate a new component named `heroes`.
|
|
|
|
<code-example language="sh" class="code-shell">
|
|
ng generate component heroes
|
|
</code-example>
|
|
|
|
The CLI creates a new folder, `src/app/heroes/`, and generates
|
|
the three files of the `HeroesComponent` along with a test file.
|
|
|
|
The `HeroesComponent` class file is as follows:
|
|
|
|
<code-example path="toh-pt1/src/app/heroes/heroes.component.ts" region="v1" header="app/heroes/heroes.component.ts (initial version)" linenums="false">
|
|
</code-example>
|
|
|
|
You always import the `Component` symbol from the Angular core library
|
|
and annotate the component class with `@Component`.
|
|
|
|
`@Component` is a decorator function that specifies the Angular metadata for the component.
|
|
|
|
The CLI generated three metadata properties:
|
|
|
|
1. `selector`— the component's CSS element selector
|
|
1. `templateUrl`— the location of the component's template file.
|
|
1. `styleUrls`— the location of the component's private CSS styles.
|
|
|
|
{@a selector}
|
|
|
|
The [CSS element selector](https://developer.mozilla.org/en-US/docs/Web/CSS/Type_selectors),
|
|
`'app-heroes'`, matches the name of the HTML element that identifies this component within a parent component's template.
|
|
|
|
The `ngOnInit()` is a [lifecycle hook](guide/lifecycle-hooks#oninit).
|
|
Angular calls `ngOnInit()` shortly after creating a component.
|
|
It's a good place to put initialization logic.
|
|
|
|
Always `export` the component class so you can `import` it elsewhere ... like in the `AppModule`.
|
|
|
|
### Add a `hero` property
|
|
|
|
Add a `hero` property to the `HeroesComponent` for a hero named "Windstorm."
|
|
|
|
<code-example path="toh-pt1/src/app/heroes/heroes.component.ts" region="add-hero" header="heroes.component.ts (hero property)" linenums="false">
|
|
</code-example>
|
|
|
|
### Show the hero
|
|
|
|
Open the `heroes.component.html` template file.
|
|
Delete the default text generated by the Angular CLI and
|
|
replace it with a data binding to the new `hero` property.
|
|
|
|
<code-example path="toh-pt1/src/app/heroes/heroes.component.1.html" header="heroes.component.html" region="show-hero-1" linenums="false">
|
|
</code-example>
|
|
|
|
## Show the `HeroesComponent` view
|
|
|
|
To display the `HeroesComponent`, you must add it to the template of the shell `AppComponent`.
|
|
|
|
Remember that `app-heroes` is the [element selector](#selector) for the `HeroesComponent`.
|
|
So add an `<app-heroes>` element to the `AppComponent` template file, just below the title.
|
|
|
|
<code-example path="toh-pt1/src/app/app.component.html" header="src/app/app.component.html" linenums="false">
|
|
</code-example>
|
|
|
|
Assuming that the CLI `ng serve` command is still running,
|
|
the browser should refresh and display both the application title and the hero name.
|
|
|
|
## Create a Hero class
|
|
|
|
A real hero is more than a name.
|
|
|
|
Create a `Hero` class in its own file in the `src/app` folder.
|
|
Give it `id` and `name` properties.
|
|
|
|
<code-example path="toh-pt1/src/app/hero.ts" header="src/app/hero.ts" linenums="false">
|
|
</code-example>
|
|
|
|
|
|
Return to the `HeroesComponent` class and import the `Hero` class.
|
|
|
|
Refactor the component's `hero` property to be of type `Hero`.
|
|
Initialize it with an `id` of `1` and the name `Windstorm`.
|
|
|
|
The revised `HeroesComponent` class file should look like this:
|
|
|
|
<code-example path="toh-pt1/src/app/heroes/heroes.component.ts" linenums="false"
|
|
header= "src/app/heroes/heroes.component.ts">
|
|
</code-example>
|
|
|
|
The page no longer displays properly because you changed the hero from a string to an object.
|
|
|
|
## Show the hero object
|
|
|
|
Update the binding in the template to announce the hero's name
|
|
and show both `id` and `name` in a details layout like this:
|
|
|
|
<code-example path="toh-pt1/src/app/heroes/heroes.component.1.html" region="show-hero-2" header="heroes.component.html (HeroesComponent's template)" linenums="false">
|
|
</code-example>
|
|
|
|
The browser refreshes and displays the hero's information.
|
|
|
|
## Format with the _UppercasePipe_
|
|
|
|
Modify the `hero.name` binding like this.
|
|
<code-example path="toh-pt1/src/app/heroes/heroes.component.html" header="src/app/heroes/heroes.component.html" region="pipe">
|
|
</code-example>
|
|
|
|
The browser refreshes and now the hero's name is displayed in capital letters.
|
|
|
|
The word `uppercase` in the interpolation binding,
|
|
right after the pipe operator ( | ),
|
|
activates the built-in `UppercasePipe`.
|
|
|
|
[Pipes](guide/pipes) are a good way to format strings, currency amounts, dates and other display data.
|
|
Angular ships with several built-in pipes and you can create your own.
|
|
|
|
## Edit the hero
|
|
|
|
Users should be able to edit the hero name in an `<input>` textbox.
|
|
|
|
The textbox should both _display_ the hero's `name` property
|
|
and _update_ that property as the user types.
|
|
That means data flows from the component class _out to the screen_ and
|
|
from the screen _back to the class_.
|
|
|
|
To automate that data flow, setup a two-way data binding between the `<input>` form element and the `hero.name` property.
|
|
|
|
### Two-way binding
|
|
|
|
Refactor the details area in the `HeroesComponent` template so it looks like this:
|
|
|
|
<code-example path="toh-pt1/src/app/heroes/heroes.component.1.html" region="name-input" header="src/app/heroes/heroes.component.html (HeroesComponent's template)" linenums="false">
|
|
|
|
</code-example>
|
|
|
|
**[(ngModel)]** is Angular's two-way data binding syntax.
|
|
|
|
Here it binds the `hero.name` property to the HTML textbox so that data can flow _in both directions:_ from the `hero.name` property to the textbox, and from the textbox back to the `hero.name`.
|
|
|
|
### The missing _FormsModule_
|
|
|
|
Notice that the app stopped working when you added `[(ngModel)]`.
|
|
|
|
To see the error, open the browser development tools and look in the console
|
|
for a message like
|
|
|
|
<code-example language="sh" class="code-shell">
|
|
Template parse errors:
|
|
Can't bind to 'ngModel' since it isn't a known property of 'input'.
|
|
</code-example>
|
|
|
|
Although `ngModel` is a valid Angular directive, it isn't available by default.
|
|
|
|
It belongs to the optional `FormsModule` and you must _opt-in_ to using it.
|
|
|
|
## _AppModule_
|
|
|
|
Angular needs to know how the pieces of your application fit together
|
|
and what other files and libraries the app requires.
|
|
This information is called _metadata_.
|
|
|
|
Some of the metadata is in the `@Component` decorators that you added to your component classes.
|
|
Other critical metadata is in [`@NgModule`](guide/ngmodules) decorators.
|
|
|
|
The most important `@NgModule` decorator annotates the top-level **AppModule** class.
|
|
|
|
The Angular CLI generated an `AppModule` class in `src/app/app.module.ts` when it created the project.
|
|
This is where you _opt-in_ to the `FormsModule`.
|
|
|
|
### Import _FormsModule_
|
|
|
|
Open `AppModule` (`app.module.ts`) and import the `FormsModule` symbol from the `@angular/forms` library.
|
|
|
|
<code-example path="toh-pt1/src/app/app.module.ts" header="app.module.ts (FormsModule symbol import)"
|
|
region="formsmodule-js-import">
|
|
</code-example>
|
|
|
|
Then add `FormsModule` to the `@NgModule` metadata's `imports` array, which contains a list of external modules that the app needs.
|
|
|
|
<code-example path="toh-pt1/src/app/app.module.ts" header="app.module.ts (@NgModule imports)"
|
|
region="ng-imports">
|
|
</code-example>
|
|
|
|
When the browser refreshes, the app should work again. You can edit the hero's name and see the changes reflected immediately in the `<h2>` above the textbox.
|
|
|
|
### Declare `HeroesComponent`
|
|
|
|
Every component must be declared in _exactly one_ [NgModule](guide/ngmodules).
|
|
|
|
_You_ didn't declare the `HeroesComponent`.
|
|
So why did the application work?
|
|
|
|
It worked because the Angular CLI declared `HeroesComponent` in the `AppModule` when it generated that component.
|
|
|
|
Open `src/app/app.module.ts` and find `HeroesComponent` imported near the top.
|
|
<code-example path="toh-pt1/src/app/app.module.ts" header="src/app/app.module.ts" region="heroes-import" >
|
|
</code-example>
|
|
|
|
The `HeroesComponent` is declared in the `@NgModule.declarations` array.
|
|
<code-example path="toh-pt1/src/app/app.module.ts" header="src/app/app.module.ts" region="declarations">
|
|
</code-example>
|
|
|
|
Note that `AppModule` declares both application components, `AppComponent` and `HeroesComponent`.
|
|
|
|
|
|
## Final code review
|
|
|
|
Your app should look like this <live-example></live-example>. Here are the code files discussed on this page.
|
|
|
|
<code-tabs>
|
|
|
|
<code-pane header="src/app/heroes/heroes.component.ts" path="toh-pt1/src/app/heroes/heroes.component.ts">
|
|
</code-pane>
|
|
|
|
<code-pane header="src/app/heroes/heroes.component.html" path="toh-pt1/src/app/heroes/heroes.component.html">
|
|
</code-pane>
|
|
|
|
<code-pane header="src/app/app.module.ts"
|
|
path="toh-pt1/src/app/app.module.ts">
|
|
</code-pane>
|
|
|
|
<code-pane header="src/app/app.component.ts" path="toh-pt1/src/app/app.component.ts">
|
|
</code-pane>
|
|
|
|
<code-pane header="src/app/app.component.html" path="toh-pt1/src/app/app.component.html">
|
|
</code-pane>
|
|
|
|
<code-pane header="src/app/hero.ts"
|
|
path="toh-pt1/src/app/hero.ts">
|
|
</code-pane>
|
|
|
|
</code-tabs>
|
|
|
|
## Summary
|
|
|
|
* You used the CLI to create a second `HeroesComponent`.
|
|
* You displayed the `HeroesComponent` by adding it to the `AppComponent` shell.
|
|
* You applied the `UppercasePipe` to format the name.
|
|
* You used two-way data binding with the `ngModel` directive.
|
|
* You learned about the `AppModule`.
|
|
* You imported the `FormsModule` in the `AppModule` so that Angular would recognize and apply the `ngModel` directive.
|
|
* You learned the importance of declaring components in the `AppModule`
|
|
and appreciated that the CLI declared it for you.
|