`添加到`AppComponent`的模板中。
Always `export` the component class because you'll always `import` it elsewhere.
总是`export`这个组件类，因为你必然会在别处`import`它。
### Hero detail template
### 英雄详情的模板
To move the hero detail view to the `HeroDetailComponent`,
cut the hero detail _content_ from the bottom of the `AppComponent` template
and paste it into a new `template` property in the `@Component` metadata.
要把英雄详情的视图移入`HeroDetailComponent`，只要把英雄详情的 *内容* 从`AppComponent`模板的底部剪切出来，
粘贴到`@Component`元数据的`template`属性中就可以了。
The `HeroDetailComponent` has a _hero_, not a _selected hero_.
Replace the word, "selectedHero", with the word, "hero", everywhere in the template.
When you're done, the new template should look like this:
`HeroDetailComponent`有一个 `hero`属性，而不再是`selectedHero`。
所以我们也要在模板中把所有的`selectedHero`替换为`hero`。
这些完成之后，新的模板是这样的：
### Add the *hero* property
### 添加`hero`属性
The `HeroDetailComponent` template binds to the component's `hero` property.
Add that property to the `HeroDetailComponent` class like this:
`HeroDetailComponent`模板绑定到了该组件的`hero`属性上。
把这个属性添加到`HeroDetailComponent`类上，就像这样：
The `hero` property is typed as an instance of `Hero`.
The `Hero` class is still in the `app.component.ts` file.
Now there are two components that need to reference the `Hero` class.
The Angular [style guide](guide/styleguide#rule-of-one "Style guide: rule of one") recommends one class per file anyway.
`hero`属性的类型是`Hero`。
`Hero`类仍然在`app.component.ts`文件中。
现在，有两个组件需要`Hero`类的引用。
而Angular[风格指南](guide/styleguide#rule-of-one "Style guide: rule of one")建议每个文件中只有一个类。
Move the `Hero` class from `app.component.ts` to its own `hero.ts` file.
因此我们要把`Hero`类从`app.component.ts`移到它自己的`hero.ts`文件中：
Now that the `Hero` class is in its own file, the `AppComponent` and the `HeroDetailComponent` have to import it.
Add the following `import` statement near the top of _both_ the `app.component.ts` and the `hero-detail.component.ts` files.
现在，`Hero`类有了自己的文件，`AppComponent` 和 `HeroDetailComponent` 就要`import`它了。
把下列`import`语句添加到`app.component.ts`和`hero-detail.component.ts`文件的顶部。
### The *hero* property is an *input* property
### *hero*属性是一个***输入***属性
[Later in this page](tutorial/toh-pt3#add-hero-detail "Add the HeroDetailComponent to the AppComponent"),
the parent `AppComponent` will tell the child `HeroDetailComponent` which hero to display
by binding its `selectedHero` to the `hero` property of the `HeroDetailComponent`.
The binding will look like this:
[在本章稍后的部分](tutorial/toh-pt3#add-hero-detail "Add the HeroDetailComponent to the AppComponent")，
父组件`AppComponent`会告诉子组件`HeroDetailComponent`要显示哪个英雄，
告诉的方法是把它的`selectedHero`属性绑定到`HeroDetailComponent`的`hero`属性上。
这种绑定是这样的：
Putting square brackets around the `hero` property, to the left of the equal sign (=),
makes it the *target* of a property binding expression.
You must declare a *target* binding property to be an *input* property.
Otherwise, Angular rejects the binding and throws an error.
在等号的左边，是方括号围绕的`hero`属性，这表示它是属性绑定表达式的*目标*。
我们要绑定到的*目标*属性必须是一个*输入*属性，否则Angular会拒绝绑定，并抛出一个错误。
First, amend the `@angular/core` import statement to include the `Input` symbol.
首先，修改`@angular/core`导入语句，使其包含符号`Input`。
Then declare that `hero` is an *input* property by
preceding it with the `@Input` decorator that you imported earlier.
然后，通过在`hero`属性前面加上`@Input`装饰器，来表明它是一个输入属性。
Read more about _input_ properties in the
[Attribute Directives](guide/attribute-directives#why-input) page.
要了解*输入属性*的更多知识，参见[属性型指令](guide/attribute-directives#why-input)页。
That's it. The `hero` property is the only thing in the `HeroDetailComponent` class.
现在，`hero`属性是`HeroDetailComponent`类中唯一的东西。
All it does is receive a hero object through its `hero` input property and then bind to that property with its template.
它所做的一切就是通过它的输入属性`hero`接收一个英雄对象，然后把这个属性绑定到自己的模板中。
Here's the complete `HeroDetailComponent`.
下面是完整的`HeroDetailComponent`：
## Declare _HeroDetailComponent_ in the _AppModule_
## 在`AppModule`中声明`HeroDetailComponent`
Every component must be declared in one—and only one—NgModule.
每个组件都必须在一个（且只有一个）Angular模块中声明。
Open `app.module.ts` in your editor and import the `HeroDetailComponent` so you can refer to it.
打开`app.module.ts`并且导入`HeroDetailComponent`，以便我们可以引用它。
Add `HeroDetailComponent` to the module's `declarations` array.
把`HeroDetailComponent`添加到该模块的`declarations`数组中。
In general, the `declarations` array contains a list of application components, pipes, and directives that belong to the module.
A component must be declared in a module before other components can reference it.
This module declares only the two application components, `AppComponent` and `HeroDetailComponent`.
通常，`declarations`数组包含应用中属于该模块的组件、管道和指令的列表。
组件在被其它组件引用之前必须先在一个模块中声明过。
这个模块只声明了两个组件：`AppComponent` 和 `HeroDetailComponent`。
Read more about NgModules in the [NgModules](guide/ngmodule "NgModules") guide.
要了解关于Angular模块的更多知识，参见[Angular模块](guide/ngmodule "Angular Modules (NgModule)")页。
{@a add-hero-detail}
## Add the _HeroDetailComponent_ to the _AppComponent_
## 把`HeroDetailComponent`添加到`AppComponent`中
The `AppComponent` is still a master/detail view.
It used to display the hero details on its own, before you cut out that portion of the template.
Now it will delegate to the `HeroDetailComponent`.
`AppComponent`仍然是主从视图。
在我们剪切模板之前，它自己显示英雄的详情。
现在，它委托给了`HeroDetailComponent`。
Recall that `hero-detail` is the CSS [`selector`](tutorial/toh-pt3#selector "HeroDetailComponent selector")
in the `HeroDetailComponent` metadata.
That's the tag name of the element that represents the `HeroDetailComponent`.
回想一下，`hero-detail`正是`HeroDetailComponent`元数据中使用的 CSS [`selector`](tutorial/toh-pt3#selector "HeroDetailComponent selector")
它是一个HTML元素的标签名，用于表示`HeroDetailComponent`。
Add a `` element near the bottom of the `AppComponent` template,
where the hero detail view used to be.
把``元素添加到`AppComponent`模板的底部，那里就是英雄详情视图所在的位置。
Coordinate the master `AppComponent` with the `HeroDetailComponent`
by binding the `selectedHero` property of the `AppComponent`
to the `hero` property of the `HeroDetailComponent`.
协调主视图`AppComponent`与`HeroDetailComponent`的方式是把`AppComponent`的`selectedHero`属性绑定到`HeroDetailComponent`的`hero`属性上。
Now every time the `selectedHero` changes, the `HeroDetailComponent` gets a new hero to display.
每当`selectedHero`变化时，`HeroDetailComponent`就会显示一个新的英雄。
The revised `AppComponent` template should look like this:
修改后的`AppComponent`模板是这样的：
## What changed?
## 有哪些变化？
As [before](tutorial/toh-pt2), whenever a user clicks on a hero name,
the hero detail appears below the hero list.
But now the `HeroDetailView` is presenting those details.
仍然像[以前](tutorial/toh-pt2)一样，一旦用户点击了英雄的名字，英雄详情就会显示在英雄列表的下方。
不过现在改用`HeroDetailView`来表示英雄详情了。
Refactoring the original `AppComponent` into two components yields benefits, both now and in the future:
我们把原来的`AppComponent`重构成了两个组件具有一些显著优点，无论是现在还是未来：
1. You simplified the `AppComponent` by reducing its responsibilities.
通过缩减`AppComponent`的职责，我们简化了它。
1. You can evolve the `HeroDetailComponent` into a rich hero editor
without touching the parent `AppComponent`.
我们将来可以把`HeroDetailComponent`改进为功能更丰富的英雄编辑器，而不用动`AppComponent`。
1. You can evolve the `AppComponent` without touching the hero detail view.
同样，我们也可以改进`AppComponent`而不用动英雄详情视图。
1. You can re-use the `HeroDetailComponent` in the template of some future parent component.
我们可以在未来的其它父组件的模板中复用`HeroDetailComponent`。
### Review the app structure
### 审视本应用的代码结构
Verify that you have the following structure:
验证它是否已经有了如下结构：
angular-tour-of-heroes
src
app
app.component.ts
app.module.ts
hero.ts
hero-detail.component.ts
main.ts
index.html
styles.css
systemjs.config.js
tsconfig.json
node_modules ...
package.json
Here are the code files discussed in this page.
下面是我们在本章讨论的代码文件：
## The road you’ve travelled
## 走过的路
Here's what you achieved in this page:
来盘点一下我们已经构建了什么。
* You created a reusable component.
我们创建了一个可复用组件
* You learned how to make a component accept input.
我们学会了如何让一个组件接收输入
* You learned to declare the required application directives in an NgModule. You
listed the directives in the `@NgModule` decorator's `declarations` array.
我们学会了在 Angular 模块中声明该应用所需的指令。
只要把这些指令列在`NgModule`装饰器的`declarations`数组中就可以了。
* You learned to bind a parent component to a child component.
我们学会了把父组件绑定到子组件。
Your app should look like this .
现在，应用应该变成了这样：。
## The road ahead
## 前方的路
The Tour of Heroes app is more reusable with shared components,
but its (mock) data is still hard coded within the `AppComponent`.
That's not sustainable.
Data access should be refactored to a separate service
and shared among the components that need data.
通过抽取共享组件，我们的《英雄指南》变得更有复用性了，但在`AppComponent`中，我们仍然使用着硬编码的模拟数据。显然，这种方式不能“可持续发展”。
我们要把数据访问逻辑重构到一个独立的服务中，并在需要数据的组件之间共享。
You’ll learn to create services in the [next tutorial](tutorial/toh-pt4 "Services") page.
在[下一步](tutorial/toh-pt4)，我们将学习如何创建服务。