angular-cn/aio/content/tutorial/toh-pt1.md

@title
The Hero Editor

@intro
Build a simple hero editor.

@description


## Setup to develop locally
Follow the [setup](guide/setup) instructions for creating a new project
named <code>angular-tour-of-heroes</code>.

The file structure should look like this:


<aio-filetree>

  <aio-folder>
    angular-tour-of-heroes
    <aio-folder>
      src
      <aio-folder>
        app
        <aio-file>
          app.component.ts
        </aio-file>

        <aio-file>
          app.module.ts
        </aio-file>

      </aio-folder>

      <aio-file>
        main.ts
      </aio-file>

      <aio-file>
        index.html
      </aio-file>

      <aio-file>
        styles.css
      </aio-file>

      <aio-file>
        systemjs.config.js
      </aio-file>

      <aio-file>
        tsconfig.json
      </aio-file>

    </aio-folder>

    <aio-file>
      node_modules ...
    </aio-file>

    <aio-file>
      package.json
    </aio-file>

  </aio-folder>

</aio-filetree>



When you're done with this page, the app should look like this <live-example></live-example>.


{@a keep-transpiling}


## Keep the app transpiling and running
Enter the following command in the terminal window:


<code-example language="sh" class="code-shell">
  npm start

</code-example>



This command runs the TypeScript compiler in "watch mode", recompiling automatically when the code changes.
The command simultaneously launches the app in a browser and refreshes the browser when the code changes.

You can keep building the Tour of Heroes without pausing to recompile or refresh the browser.



## Show the hero
Add two properties to the `AppComponent`: a `title` property for the app name and a `hero` property
for a hero named "Windstorm."


<code-example path="toh-1/app/app.component.1.ts" region="app-component-1" title="app.component.ts (AppComponent class)" linenums="false">

</code-example>



Now update the template in the `@Component` decorator with data bindings to these new properties.


<code-example path="toh-1/app/app.component.1.ts" region="show-hero" title="app.component.ts (@Component)" linenums="false">

</code-example>



The browser refreshes and displays the title and hero name.

The double curly braces are Angular's *interpolation binding* syntax.
These interpolation bindings present the component's `title` and `hero` property values,
as strings, inside the HTML header tags.


<div class="l-sub-section">



Read more about interpolation in the [Displaying Data](guide/displaying-data) page.


</div>



### Hero object

The hero needs more properties.
Convert the `hero` from a literal string to a class.

Create a `Hero` class with `id` and `name` properties.
Add these properties near the top of the `app.component.ts` file, just below the import statement.


<code-example path="toh-1/src/app/app.component.ts" region="hero-class-1" title="src/app/app.component.ts (Hero class)" linenums="false">

</code-example>



In the `Hero` class, refactor the component's `hero` property to be of type `Hero`,
then initialize it with an `id` of `1` and the name `Windstorm`.


<code-example path="toh-1/src/app/app.component.ts" region="hero-property-1" title="src/app/app.component.ts (hero property)" linenums="false">

</code-example>



Because you changed the hero from a string to an object,
update the binding in the template to refer to the hero's `name` property.


<code-example path="toh-1/app/app.component.1.ts" region="show-hero-2" title="toh-1/app/app.component.ts">

</code-example>



The browser refreshes and continues to display the hero's name.

### Adding HTML with multi-line template strings

To show all of the hero's properties,
add a `<div>` for the hero's `id` property and another `<div>` for the hero's `name`.
To keep the template readable, place each `<div>` on its own line.

The backticks around the component template let you put the `<h1>`, `<h2>`, and `<div>` elements on their own lines,
thanks to the <i>template literals</i> feature in ES2015 and TypeScript. For more information, see
<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Template_literals" target="_blank" title="template literal">Template literals</a>.



<code-example path="toh-1/app/app.component.1.ts" region="multi-line-strings" title="app.component.ts (AppComponent's template)" linenums="false">

</code-example>




## Edit the hero name

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.

You need a two-way binding between the `<input>` form element and the `hero.name` property.

### Two-way binding

Refactor the hero name in the template so it looks like this:

<code-example path="toh-1/app/app.component.1.ts" region="name-input" title="toh-1/app/app.component.ts" linenums="false">

</code-example>



`[(ngModel)]` is the Angular syntax to bind the `hero.name` property
to the textbox.
Data flows _in both directions:_ from the property to the textbox,
and from the textbox back to the property.

Unfortunately, immediately after this change, the application breaks.
If you looked in the browser console, you'd see Angular complaining that
"`ngModel` ... isn't a known property of `input`."

Although `NgModel` is a valid Angular directive, it isn't available by default.
It belongs to the optional `FormsModule`.
You must opt-in to using that module.

### Import the _FormsModule_

Open the `app.module.ts` file and import the `FormsModule` symbol from the `@angular/forms` library.
Then add the `FormsModule` to the `@NgModule` metadata's `imports` array, which contains the list
of external modules that the app uses.

The updated `AppModule` looks like this:

<code-example path="toh-1/src/app/app.module.ts" title="app.module.ts (FormsModule import)">

</code-example>



<div class="l-sub-section">



Read more about `FormsModule` and `ngModel` in the
[Two-way data binding with ngModel](guide/forms#ngModel) section of the
[Forms](guide/forms) guide and the
[Two-way binding with NgModel](guide/template-syntax#ngModel) section of the
[Template Syntax](guide/template-syntax) guide.


</div>



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.



## The road you've travelled

Take stock of what you've built.

* The Tour of Heroes app uses the double curly braces of interpolation (a type of one-way data binding)
to display the app title and properties of a `Hero` object.
* You wrote a multi-line template using ES2015's template literals to make the template readable.
* You added a two-way data binding to the `<input>` element
using the built-in `ngModel` directive. This binding both displays the hero's name and allows users to change it.
* The `ngModel` directive propagates changes to every other binding of the `hero.name`.

Your app should look like this <live-example></live-example>.

Here's the complete `app.component.ts` as it stands now:


<code-example path="toh-1/src/app/app.component.ts" title="src/app/app.component.ts">

</code-example>




## The road ahead
In the [next tutorial page](tutorial/toh-pt2), you'll build on the Tour of Heroes app to display a list of heroes.
You'll also allow the user to select heroes and display their details.
You'll learn more about how to retrieve lists and bind them to the template.