197 lines
11 KiB
Markdown
197 lines
11 KiB
Markdown
# Feature Modules
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# 特性模块
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Feature modules are NgModules for the purpose of organizing code.
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特性模块是用来对代码进行组织的模块。
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#### Prerequisites
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#### 前提条件
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A basic understanding of the following:
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对下列知识有基本的了解：
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* [Bootstrapping](guide/bootstrapping).
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[引导启动](guide/bootstrapping)。
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* [JavaScript Modules vs. NgModules](guide/ngmodule-vs-jsmodule).
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[JavaScript 模块与 NgModules](guide/ngmodule-vs-jsmodule)。
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* [Frequently Used Modules](guide/frequent-ngmodules).
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[常用模块](guide/frequent-ngmodules)。
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For the final sample app with a feature module that this page describes,
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see the <live-example></live-example>.
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要想查看本页提到的这个带有特性模块的范例应用，参见 <live-example></live-example>。
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<hr>
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As your app grows, you can organize code relevant for a specific feature.
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This helps apply clear boundaries for features. With feature modules,
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you can keep code related to a specific functionality or feature
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separate from other code. Delineating areas of your
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app helps with collaboration between developers and teams, separating
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directives, and managing the size of the root module.
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随着应用的增长，你可能需要组织与特定应用有关的代码。
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这将帮你把特性划出清晰的边界。使用特性模块，你可以把与特定的功能或特性有关的代码从其它代码中分离出来。
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为应用勾勒出清晰的边界，有助于开发人员之间、小组之间的协作，有助于分离各个指令，并帮助管理根模块的大小。
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## Feature modules vs. root modules
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## 特性模块 vs. 根模块
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A feature module is an organizational best practice, as opposed to a concept of the core Angular API. A feature module delivers a cohesive set of functionality focused on a
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specific application need such as a user workflow, routing, or forms.
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While you can do everything within the root module, feature modules
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help you partition the app into focused areas. A feature module
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collaborates with the root module and with other modules through
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the services it provides and the components, directives, and
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pipes that it shares.
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与核心的 Angular API 的概念相反，特性模块是最佳的组织方式。特性模块提供了聚焦于特定应用需求的一组功能，比如用户工作流、路由或表单。
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虽然你也可以用根模块做完所有事情，不过特性模块可以帮助你把应用划分成一些聚焦的功能区。特性模块通过它提供的服务以及共享出的组件、指令和管道来与根模块和其它模块合作。
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## How to make a feature module
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## 如何制作特性模块
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Assuming you already have a CLI generated app, create a feature
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module using the CLI by entering the following command in the
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root project directory. Replace `CustomerDashboard` with the
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name of your module. You can omit the "Module" suffix from the name because the CLI appends it:
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如果你已经有了 CLI 生成的应用，可以在项目的根目录下输入下面的命令来创建特性模块。把这里的 `CustomerDashboard` 替换成你的模块名。你可以从名字中省略掉“Module”后缀，因为 CLI 会自动追加上它：
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```sh
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ng generate module CustomerDashboard
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```
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This causes the CLI to create a folder called `customer-dashboard` with a file inside called `customer-dashboard.module.ts` with the following contents:
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这会让 CLI 创建一个名叫 `customer-dashboard` 的文件夹，其中有一个名叫 `customer-dashboard.module.ts`，内容如下：
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```typescript
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import { NgModule } from '@angular/core';
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import { CommonModule } from '@angular/common';
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@NgModule({
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imports: [
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CommonModule
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],
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declarations: []
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})
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export class CustomerDashboardModule { }
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```
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The structure of an NgModule is the same whether it is a root module or a feature module. In the CLI generated feature module, there are two JavaScript import statements at the top of the file: the first imports `NgModule`, which, like the root module, lets you use the `@NgModule` decorator; the second imports `CommonModule`, which contributes many common directives such as `ngIf` and `ngFor`. Feature modules import `CommonModule` instead of `BrowserModule`, which is only imported once in the root module. `CommonModule` only contains information for common directives such as `ngIf` and `ngFor` which are needed in most templates, whereas `BrowserModule` configures the Angular app for the browser which needs to be done only once.
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无论根模块还是特性模块，其 NgModule 结构都是一样的。在 CLI 生成的特性模块中，在文件顶部有两个 JavaScript 的导入语句：第一个导入了 `NgModule`，它像根模块中一样让你能使用 `@NgModule` 装饰器；第二个导入了 `CommonModule`，它提供了很多像 `ngIf` 和 `ngFor` 这样的常用指令。
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特性模块导入 `CommonModule`，而不是 `BrowserModule`，后者只应该在根模块中导入一次。
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`CommonModule` 只包含常用指令的信息，比如 `ngIf` 和 `ngFor`，它们在大多数模板中都要用到，而 `BrowserModule` 为浏览器所做的应用配置只会使用一次。
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The `declarations` array is available for you to add declarables, which
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are components, directives, and pipes that belong exclusively to this particular module. To add a component, enter the following command at the command line where `customer-dashboard` is the directory where the CLI generated the feature module and `CustomerDashboard` is the name of the component:
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`declarations` 数组让你能添加专属于这个模块的可声明对象（组件、指令和管道）。
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要添加组件，就在命令行中输入如下命令，这里的 `customer-dashboard` 是一个目录，CLI 会把特性模块生成在这里，而 `CustomerDashboard` 就是该组件的名字：
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```sh
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ng generate component customer-dashboard/CustomerDashboard
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```
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This generates a folder for the new component within the customer-dashboard folder and updates the feature module with the `CustomerDashboardComponent` info:
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这会在 `customer-dashboard` 中为新组件生成一个目录，并使用 `CustomerDashboardComponent` 的信息修改这个特性模块：
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<code-example path="feature-modules/src/app/customer-dashboard/customer-dashboard.module.ts" region="customer-dashboard-component" title="src/app/customer-dashboard/customer-dashboard.module.ts" linenums="false">
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</code-example>
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The `CustomerDashboardComponent` is now in the JavaScript import list at the top and added to the `declarations` array, which lets Angular know to associate this new component with this feature module.
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`CustomerDashboardComponent` 出现在了顶部的 JavaScript 导入列表里，并且被添加到了 `declarations` 数组中，它会让 Angular 把新组件和这个特性模块联系起来。
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## Importing a feature module
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## 导入特性模块
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To incorporate the feature module into your app, you have to let the root module, `app.module.ts`, know about it. Notice the `CustomerDashboardModule` export at the bottom of `customer-dashboard.module.ts`. This exposes it so that other modules can get to it. To import it into the `AppModule`, add it to the imports in `app.module.ts` and to the `imports` array:
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要想把这个特性模块包含进应用中，你还得让根模块 `app.module.ts` 知道它。注意，在 `customer-dashboard.module.ts` 的底部导出了 `CustomerDashboardModule`。这样就把它暴露出来，以便其它模块可以拿到它。要想把它导入到 `AppModule` 中，就把它加入 `app.module.ts` 的导入表中，并将其加入 `imports` 数组：
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<code-example path="feature-modules/src/app/app.module.ts" region="app-module" title="src/app/app.module.ts" linenums="false">
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</code-example>
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Now the `AppModule` knows about the feature module. If you were to add any service providers to the feature module, `AppModule` would know about those too, as would any other feature modules. However, NgModules don’t expose their components.
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现在 `AppModule` 知道这个特性模块了。如果你往该特性模块中加入过任何服务提供商，`AppModule` 也同样会知道它，其它模块中也一样。不过，NgModule 并不会暴露出它们的组件。
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## Rendering a feature module’s component template
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## 渲染特性模块的组件模板
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When the CLI generated the `CustomerDashboardComponent` for the feature module, it included a template, `customer-dashboard.component.html`, with the following markup:
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当 CLI 为这个特性模块生成 `CustomerDashboardComponent` 时，还包含一个模板 `customer-dashboard.component.html`，它带有如下页面脚本：
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<code-example path="feature-modules/src/app/customer-dashboard/customer-dashboard/customer-dashboard.component.html" region="feature-template" title="src/app/customer-dashboard/customer-dashboard/customer-dashboard.component.html" linenums="false">
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</code-example>
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To see this HTML in the `AppComponent`, you first have to export the `CustomerDashboardComponent` in the `CustomerDashboardModule`. In `customer-dashboard.module.ts`, just beneath the `declarations` array, add an `exports` array containing `CustomerDashboardModule`:
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要想在 `AppComponent` 中查看这些 HTML，你首先要在 `CustomerDashboardModule` 中导出 `CustomerDashboardComponent`。
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在 `customer-dashboard.module.ts` 中，`declarations` 数组的紧下方，加入一个包含 `CustomerDashboardModule` 的 `exports` 数组：
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<code-example path="feature-modules/src/app/customer-dashboard/customer-dashboard.module.ts" region="component-exports" title="src/app/customer-dashboard/customer-dashboard.module.ts" linenums="false">
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</code-example>
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Next, in the `AppComponent`, `app.component.html`, add the tag `<app-customer-dashboard>`:
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然后，在 `AppComponent` 的 `app.component.html` 中，加入标签 `<app-customer-dashboard>`：
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<code-example path="feature-modules/src/app/app.component.html" region="app-component-template" title="src/app/app.component.html" linenums="false">
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</code-example>
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Now, in addition to the title that renders by default, the `CustomerDashboardComponent` template renders too:
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现在，除了默认渲染出的标题外，还渲染出了 `CustomerDashboardComponent` 的模板：
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<figure>
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<img src="generated/images/guide/feature-modules/feature-module.png" alt="feature module component">
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</figure>
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<hr />
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## More on NgModules
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## 关于 NgModule 的更多知识
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You may also be interested in the following:
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你可能还对下列内容感兴趣：
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* [Lazy Loading Modules with the Angular Router](guide/lazy-loading-ngmodules).
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[使用 Angular 路由器惰性加载模块](guide/lazy-loading-ngmodules)。
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* [Providers](guide/providers).
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[服务提供商](guide/providers)。
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* [Types of Feature Modules](guide/module-types).
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[特性模块的分类](guide/module-types)。
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