646 lines
20 KiB
Markdown
646 lines
20 KiB
Markdown
@title
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多个组件
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@intro
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把主从结构的页面重构成多个组件
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@description
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The `AppComponent` is doing _everything_ at the moment.
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In the beginning, it showed details of a single hero.
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Then it became a master/detail form with both a list of heroes and the hero detail.
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Soon there will be new requirements and capabilities.
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You can't keep piling features on top of features in one component; that's not maintainable.
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此刻，`AppComponent`负责*所有事*。
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起初，它只显示单个英雄的详情。然后，它变成了主从结构，同时显示英雄列表和一个英雄详情。
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现在，我们很快又会有新需求了。
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我们不能把这些需求全都放在一个组件中，否则将不可维护。
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You'll need to break it up into sub-components, each focused on a specific task or workflow.
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Eventually, the `AppComponent` could become a simple shell that hosts those sub-components.
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我们要把它拆分成一些子组件，每个子组件只聚焦在一个特定的任务或工作流上。
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最后，`AppComponent`将会变成一个简单的壳，用来作为那些子组件的宿主。
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In this page, you'll take the first step in that direction by carving out the hero details into a separate, reusable component.
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When you're done, the app should look like this <live-example></live-example>.
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本章中，我们要做的第一步就是把英雄详情拆分到一个独立的、可复用的组件中。
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做完这些，应用是这样的：<live-example></live-example>。
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## Where you left off
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## 延续上一步教程
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Before getting started on this page, verify that you have the following structure from earlier in the Tour of Heroes.
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If not, go back to the previous pages.
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在继续《英雄指南》之前，先检查一下，是否已经有了如下目录结构。如果没有，回上一章，看看错过了哪里。
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<div class='filetree'>
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<div class='file'>
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angular-tour-of-heroes
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</div>
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<div class='children'>
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<div class='file'>
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src
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</div>
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<div class='children'>
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<div class='file'>
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app
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</div>
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<div class='children'>
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<div class='file'>
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app.component.ts
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</div>
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<div class='file'>
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app.module.ts
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</div>
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</div>
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<div class='file'>
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main.ts
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</div>
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<div class='file'>
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index.html
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</div>
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<div class='file'>
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styles.css
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</div>
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<div class='file'>
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systemjs.config.js
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</div>
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<div class='file'>
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tsconfig.json
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</div>
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</div>
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<div class='file'>
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node_modules ...
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</div>
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<div class='file'>
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package.json
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</div>
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</div>
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</div>
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Keep the app transpiling and running while you build the Tour of Heroes
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by entering the `npm start` command in a terminal window
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[as you did before](tutorial/toh-pt1#keep-transpiling "Keep the app running").
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[像以前一样](tutorial/toh-pt1#keep-transpiling "Keep the app running")，在终端窗口中输入`npm start`命令，以便在构建《英雄指南》时保持持续转译和运行。
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## Make a hero detail component
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## 制作英雄详情组件
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Add a file named `hero-detail.component.ts` to the `app/` folder.
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This file will hold the new `HeroDetailComponent`.
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往`app/`文件夹下添加一个名叫`hero-detail.component.ts`的文件。这个文件中会存放这个新的`HeroDetailComponent`。
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The file and component names follow the standard described in the Angular
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[style guide](guide/styleguide#naming).
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文件名和组件名遵循[风格指南](guide/styleguide#naming)中的标准方式。
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* The component _class_ name should be written in _upper camel case_ and end in the word "Component".
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The hero detail component class is `HeroDetailComponent`.
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组件的类名应该是*大驼峰形式*，并且以`Component`结尾。
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因此英雄详情组件的类名是`HeroDetailComponent`。
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* The component _file_ name should be spelled in [_lower dash case_](guide/glossary#dash-case),
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each word separated by dashes, and end in `.component.ts`.
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The `HeroDetailComponent` class goes in the `hero-detail.component.ts` file.
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组件的文件名应该是[小写中线形式](guide/glossary#dash-case)，每个单词之间用中线分隔，并且以`.component.ts`结尾。
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因此`HeroDetailComponent`类应该放在`hero-detail.component.ts`文件中。
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Start writing the `HeroDetailComponent` as follows:
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`HeroDetailComponent`的代码如下：
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<code-example path="toh-pt3/app/hero-detail.component.1.ts" region="v1" title="app/hero-detail.component.ts (initial version)" linenums="false">
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</code-example>
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{@a selector}
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To define a component, you always import the `Component` symbol.
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要定义一个组件，我们总是要先导入符号`Component`。
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The `@Component` decorator provides the Angular metadata for the component.
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The CSS selector name, `hero-detail`, will match the element tag
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that identifies this component within a parent component's template.
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[Near the end of this tutorial page](tutorial/toh-pt3#add-hero-detail "Add the HeroDetailComponent to the AppComponent"),
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you'll add a `<hero-detail>` element to the `AppComponent` template.
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`@Component`装饰器为组件提供了Angular元数据。
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CSS选择器的名字`hero-detail`会匹配元素的标签名，用于在父组件的模板中标记出当前组件的位置。
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[本章的最后](tutorial/toh-pt3#add-hero-detail "Add the HeroDetailComponent to the AppComponent")，我们会把`<hero-detail>`添加到`AppComponent`的模板中。
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Always `export` the component class because you'll always `import` it elsewhere.
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总是`export`这个组件类，因为你必然会在别处`import`它。
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### Hero detail template
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### 英雄详情的模板
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To move the hero detail view to the `HeroDetailComponent`,
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cut the hero detail _content_ from the bottom of the `AppComponent` template
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and paste it into a new `template` property in the `@Component` metadata.
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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，
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粘贴到`@Component`元数据的`template`属性中就可以了。
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The `HeroDetailComponent` has a _hero_, not a _selected hero_.
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Replace the word, "selectedHero", with the word, "hero", everywhere in the template.
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When you're done, the new template should look like this:
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`HeroDetailComponent`有一个 `hero`属性，而不再是`selectedHero`。
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所以我们也要在模板中把所有的`selectedHero`替换为`hero`。
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这些完成之后，新的模板是这样的：
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<code-example path="toh-pt3/src/app/hero-detail.component.ts" region="template" title="src/app/hero-detail.component.ts (template)" linenums="false">
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</code-example>
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### Add the *hero* property
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### 添加`hero`属性
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The `HeroDetailComponent` template binds to the component's `hero` property.
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Add that property to the `HeroDetailComponent` class like this:
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`HeroDetailComponent`模板绑定到了该组件的`hero`属性上。
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把这个属性添加到`HeroDetailComponent`类上，就像这样：
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<code-example path="toh-pt3/app/hero-detail.component.1.ts" region="hero" title="src/app/hero-detail.component.ts (hero property)">
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</code-example>
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The `hero` property is typed as an instance of `Hero`.
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The `Hero` class is still in the `app.component.ts` file.
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Now there are two components that need to reference the `Hero` class.
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The Angular [style guide](guide/styleguide#rule-of-one "Style guide: rule of one") recommends one class per file anyway.
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`hero`属性的类型是`Hero`。
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`Hero`类仍然在`app.component.ts`文件中。
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现在，有两个组件需要`Hero`类的引用。
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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。
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Move the `Hero` class from `app.component.ts` to its own `hero.ts` file.
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因此我们要把`Hero`类从`app.component.ts`移到它自己的`hero.ts`文件中：
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<code-example path="toh-pt3/src/app/hero.ts" title="src/app/hero.ts" linenums="false">
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</code-example>
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Now that the `Hero` class is in its own file, the `AppComponent` and the `HeroDetailComponent` have to import it.
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Add the following `import` statement near the top of _both_ the `app.component.ts` and the `hero-detail.component.ts` files.
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现在，`Hero`类有了自己的文件，`AppComponent` 和 `HeroDetailComponent` 就要`import`它了。
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把下列`import`语句添加到`app.component.ts`和`hero-detail.component.ts`文件的顶部。
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<code-example path="toh-pt3/app/hero-detail.component.1.ts" region="hero-import" title="src/app/hero-detail.component.ts">
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</code-example>
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### The *hero* property is an *input* property
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### *hero*属性是一个***输入***属性
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[Later in this page](tutorial/toh-pt3#add-hero-detail "Add the HeroDetailComponent to the AppComponent"),
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the parent `AppComponent` will tell the child `HeroDetailComponent` which hero to display
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by binding its `selectedHero` to the `hero` property of the `HeroDetailComponent`.
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The binding will look like this:
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[在本章稍后的部分](tutorial/toh-pt3#add-hero-detail "Add the HeroDetailComponent to the AppComponent")，
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父组件`AppComponent`会告诉子组件`HeroDetailComponent`要显示哪个英雄，
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告诉的方法是把它的`selectedHero`属性绑定到`HeroDetailComponent`的`hero`属性上。
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这种绑定是这样的：
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<code-example path="toh-pt3/app/app.component.1.html" region="hero-detail-binding" title="src/app/app.component.html" linenums="false">
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</code-example>
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Putting square brackets around the `hero` property, to the left of the equal sign (=),
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makes it the *target* of a property binding expression.
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You must declare a *target* binding property to be an *input* property.
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Otherwise, Angular rejects the binding and throws an error.
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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*。
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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。
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First, amend the `@angular/core` import statement to include the `Input` symbol.
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首先，修改`@angular/core`导入语句，使其包含符号`Input`。
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<code-example path="toh-pt3/src/app/hero-detail.component.ts" region="import-input" title="src/app/hero-detail.component.ts (excerpt)" linenums="false">
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</code-example>
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Then declare that `hero` is an *input* property by
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preceding it with the `@Input` decorator that you imported earlier.
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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。
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<code-example path="toh-pt3/src/app/hero-detail.component.ts" region="hero" title="src/app/hero-detail.component.ts (excerpt)" linenums="false">
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</code-example>
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<div class="l-sub-section">
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Read more about _input_ properties in the
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[Attribute Directives](guide/attribute-directives#why-input) page.
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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。
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</div>
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That's it. The `hero` property is the only thing in the `HeroDetailComponent` class.
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现在，`hero`属性是`HeroDetailComponent`类中唯一的东西。
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<code-example path="toh-pt3/src/app/hero-detail.component.ts" region="class" title="src/src/app/hero-detail.component.ts" linenums="false">
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</code-example>
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All it does is receive a hero object through its `hero` input property and then bind to that property with its template.
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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。
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Here's the complete `HeroDetailComponent`.
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下面是完整的`HeroDetailComponent`：
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<code-example path="toh-pt3/src/app/hero-detail.component.ts" title="src/app/hero-detail.component.ts">
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</code-example>
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## Declare _HeroDetailComponent_ in the _AppModule_
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## 在`AppModule`中声明`HeroDetailComponent`
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Every component must be declared in one—and only one—NgModule.
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每个组件都必须在一个（且只有一个）Angular模块中声明。
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Open `app.module.ts` in your editor and import the `HeroDetailComponent` so you can refer to it.
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打开`app.module.ts`并且导入`HeroDetailComponent`，以便我们可以引用它。
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<code-example path="toh-pt3/src/app/app.module.ts" region="hero-detail-import" title="src/app/app.module.ts">
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</code-example>
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Add `HeroDetailComponent` to the module's `declarations` array.
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把`HeroDetailComponent`添加到该模块的`declarations`数组中。
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<code-example path="toh-pt3/src/app/app.module.ts" region="declarations" title="src/app/app.module.ts" linenums="false">
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</code-example>
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In general, the `declarations` array contains a list of application components, pipes, and directives that belong to the module.
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A component must be declared in a module before other components can reference it.
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This module declares only the two application components, `AppComponent` and `HeroDetailComponent`.
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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。
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组件在被其它组件引用之前必须先在一个模块中声明过。
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这个模块只声明了两个组件：`AppComponent` 和 `HeroDetailComponent`。
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<div class="l-sub-section">
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Read more about NgModules in the [NgModules](guide/ngmodule "NgModules") guide.
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要了解关于Angular模块的更多知识，参见[Angular模块](guide/ngmodule "Angular Modules (NgModule)")页。
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</div>
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{@a add-hero-detail}
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## Add the _HeroDetailComponent_ to the _AppComponent_
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## 把`HeroDetailComponent`添加到`AppComponent`中
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The `AppComponent` is still a master/detail view.
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It used to display the hero details on its own, before you cut out that portion of the template.
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Now it will delegate to the `HeroDetailComponent`.
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`AppComponent`仍然是主从视图。
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在我们剪切模板之前，它自己显示英雄的详情。
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现在，它委托给了`HeroDetailComponent`。
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Recall that `hero-detail` is the CSS [`selector`](tutorial/toh-pt3#selector "HeroDetailComponent selector")
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in the `HeroDetailComponent` metadata.
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That's the tag name of the element that represents the `HeroDetailComponent`.
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回想一下，`hero-detail`正是`HeroDetailComponent`元数据中使用的 CSS [`selector`](tutorial/toh-pt3#selector "HeroDetailComponent selector")
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它是一个HTML元素的标签名，用于表示`HeroDetailComponent`。
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Add a `<hero-detail>` element near the bottom of the `AppComponent` template,
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where the hero detail view used to be.
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把`<hero-detail>`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。
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Coordinate the master `AppComponent` with the `HeroDetailComponent`
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by binding the `selectedHero` property of the `AppComponent`
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to the `hero` property of the `HeroDetailComponent`.
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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。
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<code-example path="toh-pt3/app/app.component.1.html" region="hero-detail-binding" title="app.component.ts (excerpt)" linenums="false">
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</code-example>
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Now every time the `selectedHero` changes, the `HeroDetailComponent` gets a new hero to display.
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每当`selectedHero`变化时，`HeroDetailComponent`就会显示一个新的英雄。
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The revised `AppComponent` template should look like this:
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修改后的`AppComponent`模板是这样的：
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<code-example path="toh-pt3/src/app/app.component.ts" region="hero-detail-template" title="app.component.ts (excerpt)" linenums="false">
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</code-example>
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## What changed?
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## 有哪些变化？
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As [before](tutorial/toh-pt2), whenever a user clicks on a hero name,
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the hero detail appears below the hero list.
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But now the `HeroDetailView` is presenting those details.
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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：
|
||
|
||
|
||
<div class='filetree'>
|
||
|
||
<div class='file'>
|
||
angular-tour-of-heroes
|
||
</div>
|
||
|
||
<div class='children'>
|
||
|
||
<div class='file'>
|
||
src
|
||
</div>
|
||
|
||
<div class='children'>
|
||
|
||
<div class='file'>
|
||
app
|
||
</div>
|
||
|
||
<div class='children'>
|
||
|
||
<div class='file'>
|
||
app.component.ts
|
||
</div>
|
||
|
||
<div class='file'>
|
||
app.module.ts
|
||
</div>
|
||
|
||
<div class='file'>
|
||
hero.ts
|
||
</div>
|
||
|
||
<div class='file'>
|
||
hero-detail.component.ts
|
||
</div>
|
||
|
||
</div>
|
||
|
||
<div class='file'>
|
||
main.ts
|
||
</div>
|
||
|
||
<div class='file'>
|
||
index.html
|
||
</div>
|
||
|
||
<div class='file'>
|
||
styles.css
|
||
</div>
|
||
|
||
<div class='file'>
|
||
systemjs.config.js
|
||
</div>
|
||
|
||
<div class='file'>
|
||
tsconfig.json
|
||
</div>
|
||
|
||
</div>
|
||
|
||
<div class='file'>
|
||
node_modules ...
|
||
</div>
|
||
|
||
<div class='file'>
|
||
package.json
|
||
</div>
|
||
|
||
</div>
|
||
|
||
</div>
|
||
|
||
|
||
|
||
Here are the code files discussed in this page.
|
||
|
||
下面是我们在本章讨论的代码文件：
|
||
|
||
|
||
<code-tabs>
|
||
|
||
<code-pane title="src/app/hero-detail.component.ts" path="toh-pt3/src/app/hero-detail.component.ts">
|
||
|
||
</code-pane>
|
||
|
||
<code-pane title="src/app/app.component.ts" path="toh-pt3/src/app/app.component.ts">
|
||
|
||
</code-pane>
|
||
|
||
<code-pane title="src/app/hero.ts" path="toh-pt3/src/app/hero.ts">
|
||
|
||
</code-pane>
|
||
|
||
<code-pane title="src/app/app.module.ts" path="toh-pt3/src/app/app.module.ts">
|
||
|
||
</code-pane>
|
||
|
||
</code-tabs>
|
||
|
||
|
||
|
||
|
||
## Summary
|
||
|
||
## 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 <live-example></live-example>.
|
||
|
||
现在，应用应该变成了这样：<live-example></live-example>。
|
||
|
||
|
||
|
||
## Next step
|
||
|
||
## 下一步
|
||
|
||
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。 |