angular-cn/aio/content/tutorial/toh-pt3.md

Master/Detail Components

主从组件

At the moment, the HeroesComponent displays both the list of heroes and the selected hero's details.

此刻，HeroesComponent 同时显示了英雄列表和所选英雄的详情。

Keeping all features in one component as the application grows will not be maintainable. You'll want to split up large components into smaller sub-components, each focused on a specific task or workflow.

把所有特性都放在同一个组件中，将会使应用“长大”后变得不可维护。 你要把大型组件拆分成小一点的子组件，每个子组件都要集中精力处理某个特定的任务或工作流。

In this page, you'll take the first step in that direction by moving the hero details into a separate, reusable HeroDetailComponent.

本页面中，你将迈出第一步 —— 把英雄详情移入一个独立的、可复用的 HeroDetailComponent。

The HeroesComponent will only present the list of heroes. The HeroDetailComponent will present details of a selected hero.

HeroesComponent 将仅仅用来表示英雄列表。 HeroDetailComponent 将用来表示所选英雄的详情。

Make the HeroDetailComponent

制作 HeroDetailComponent

Use the Angular CLI to generate a new component named hero-detail.

使用 Angular CLI 生成一个名叫 hero-detail 的新组件。

ng generate component hero-detail

The command scaffolds the HeroDetailComponent files and declares the component in AppModule.

该命令会生成 HeroDetailComponent 文件的脚手架，并把它声明在 AppModule 中。

Write the template

编写模板

Cut the HTML for the hero detail from the bottom of the HeroesComponent template and paste it over the generated boilerplate in the HeroDetailComponent template.

从 HeroesComponent 模板的底部把表示英雄详情的 HTML 代码剪切粘贴到所生成的 HeroDetailComponent 模板中。

The pasted HTML refers to a selectedHero. The new HeroDetailComponent can present any hero, not just a selected hero. So replace "selectedHero" with "hero" everywhere in the template.

所粘贴的 HTML 引用了 selectedHero。 新的 HeroDetailComponent 可以展示任意英雄，而不仅仅所选的。因此还要把模板中的所有 selectedHero 替换为 hero。

When you're done, the HeroDetailComponent template should look like this:

完工之后，HeroDetailComponent 的模板应该是这样的：

Add the @Input() hero property

添加 @Input() hero 属性

The HeroDetailComponent template binds to the component's hero property which is of type Hero.

HeroDetailComponent 模板中绑定了组件中的 hero 属性，它的类型是 Hero。

Open the HeroDetailComponent class file and import the Hero symbol.

打开 HeroDetailComponent 类文件，并导入 Hero 符号。

The hero property must be an Input property, annotated with the @Input() decorator, because the external HeroesComponent will bind to it like this.

hero 属性必须是一个带有@Input()装饰器的输入属性，因为外部的 HeroesComponent 组件将会绑定到它。就像这样：

Amend the @angular/core import statement to include the Input symbol.

修改 @angular/core 的导入语句，导入 Input 符号。

Add a hero property, preceded by the @Input() decorator.

添加一个带有 @Input() 装饰器的 hero 属性。

That's the only change you should make to the HeroDetailComponent class. There are no more properties. There's no presentation logic. This component simply receives a hero object through its hero property and displays it.

这就是你要对 HeroDetailComponent 类做的唯一一项修改。 没有其它属性，也没有展示逻辑。这个组件所做的只是通过 hero 属性接收一个英雄对象，并显示它。

Show the HeroDetailComponent

显示 HeroDetailComponent

The HeroesComponent is still a master/detail view.

HeroesComponent 仍然是主从视图。

It used to display the hero details on its own, before you cut that portion of the template. Now it will delegate to the HeroDetailComponent.

在你从模板中剪切走代码之前，它自己负责显示英雄的详情。现在它要把这个职责委托给 HeroDetailComponent 了。

The two components will have a parent/child relationship. The parent HeroesComponent will control the child HeroDetailComponent by sending it a new hero to display whenever the user selects a hero from the list.

这两个组件将会具有父子关系。 当用户从列表中选择了某个英雄时，父组件 HeroesComponent 将通过把要显示的新英雄发送给子组件 HeroDetailComponent，来控制子组件。

You won't change the HeroesComponent class but you will change its template.

你不用修改 HeroesComponent 类，但是要修改它的模板。

{@a heroes-component-template}

Update the HeroesComponent template

修改 HeroesComponent 的模板

The HeroDetailComponent selector is 'app-hero-detail'. Add an <app-hero-detail> element near the bottom of the HeroesComponent template, where the hero detail view used to be.

HeroDetailComponent 的选择器是 'app-hero-detail'。 把 <app-hero-detail> 添加到 HeroesComponent 模板的底部，以便把英雄详情的视图显示到那里。

Bind the HeroesComponent.selectedHero to the element's hero property like this.

把 HeroesComponent.selectedHero 绑定到钙元素的 hero 属性，就像这样：

[hero]="selectedHero" is an Angular property binding.

[hero]="selectedHero" 是 Angular 的属性绑定语法。

It's a one way data binding from the selectedHero property of the HeroesComponent to the hero property of the target element, which maps to the hero property of the HeroDetailComponent.

这是一种单向数据绑定。从 HeroesComponent 的 selectedHero 属性绑定到目标元素的 hero 属性，并映射到了 HeroDetailComponent 的 hero 属性。

Now when the user clicks a hero in the list, the selectedHero changes. When the selectedHero changes, the property binding updates hero and the HeroDetailComponent displays the new hero.

现在，当用户在列表中点击某个英雄时，selectedHero 就改变了。 当 selectedHero 改变时，属性绑定会修改 HeroDetailComponent 的 hero 属性，HeroDetailComponent 就会显示这个新的英雄。

The revised HeroesComponent template should look like this:

修改后的 HeroesComponent 的模板是这样的：

The browser refreshes and the app starts working again as it did before.

浏览器刷新，应用又像以前一样开始工作了。

What changed?

有哪些变化？

As before, whenever a user clicks on a hero name, the hero detail appears below the hero list. Now the HeroDetailComponent is presenting those details instead of the HeroesComponent.

像以前一样，一旦用户点击了一个英雄的名字，该英雄的详情就显示在了英雄列表下方。 现在，HeroDetailComponent 负责显示那些详情，而不再是 HeroesComponent。

Refactoring the original HeroesComponent into two components yields benefits, both now and in the future:

把原来的 HeroesComponent 重构成两个组件带来了一些优点，无论是现在还是未来：

1. You simplified the HeroesComponent by reducing its responsibilities.

   你通过缩减 HeroesComponent 的职责简化了该组件。

2. You can evolve the HeroDetailComponent into a rich hero editor without touching the parent HeroesComponent.

   你可以把 HeroDetailComponent 改进成一个功能丰富的英雄编辑器，而不用改动父组件 HeroesComponent。

3. You can evolve the HeroesComponent without touching the hero detail view.

   你可以改进 HeroesComponent，而不用改动英雄详情视图。

4. You can re-use the HeroDetailComponent in the template of some future component.

   将来你可以在其它组件的模板中重复使用 HeroDetailComponent。

Final code review

查看最终代码

Here are the code files discussed on this page and your app should look like this .

你的应用应该变成了这样 。本页所提及的代码文件如下：

Summary

小结

• You created a separate, reusable HeroDetailComponent.

  你创建了一个独立的、可复用的 HeroDetailComponent 组件。

• You used a property binding to give the parent HeroesComponent control over the child HeroDetailComponent.

  你用属性绑定语法来让父组件 HeroesComponent 可以控制子组件 HeroDetailComponent。

• You used the @Input decorator to make the hero property available for binding by the external HeroesComponent.

  你用 @Input 装饰器来让 hero 属性可以在外部的 HeroesComponent 中绑定。