68 lines
3.4 KiB
Markdown
68 lines
3.4 KiB
Markdown
# NgModules
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**NgModules** configure the injector and the compiler and help organize related things together.
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An NgModule is a class marked by the `@NgModule` decorator.
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`@NgModule` takes a metadata object that describes how to compile a component's template and how to create an injector at runtime.
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It identifies the module's own components, directives, and pipes,
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making some of them public, through the `exports` property, so that external components can use them.
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`@NgModule` can also add service providers to the application dependency injectors.
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For an example app showcasing all the techniques that NgModules related pages
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cover, see the <live-example></live-example>. For explanations on the individual techniques, visit the relevant NgModule pages under the NgModules
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section.
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## Angular modularity
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Modules are a great way to organize an application and extend it with capabilities from external libraries.
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Angular libraries are NgModules, such as `FormsModule`, `HttpClientModule`, and `RouterModule`.
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Many third-party libraries are available as NgModules such as
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<a href="https://material.angular.io/">Material Design</a>,
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<a href="http://ionicframework.com/">Ionic</a>, and
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<a href="https://github.com/angular/angularfire2">AngularFire2</a>.
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NgModules consolidate components, directives, and pipes into
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cohesive blocks of functionality, each focused on a
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feature area, application business domain, workflow, or common collection of utilities.
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Modules can also add services to the application.
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Such services might be internally developed, like something you'd develop yourself or come from outside sources, such as the Angular router and HTTP client.
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Modules can be loaded eagerly when the application starts or lazy loaded asynchronously by the router.
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NgModule metadata does the following:
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* Declares which components, directives, and pipes belong to the module.
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* Makes some of those components, directives, and pipes public so that other module's component templates can use them.
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* Imports other modules with the components, directives, and pipes that components in the current module need.
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* Provides services that the other application components can use.
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Every Angular app has at least one module, the root module.
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You [bootstrap](guide/bootstrapping) that module to launch the application.
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The root module is all you need in a simple application with a few components.
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As the app grows, you refactor the root module into [feature modules](guide/feature-modules)
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that represent collections of related functionality.
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You then import these modules into the root module.
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## The basic NgModule
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The [Angular CLI](cli) generates the following basic `AppModule` when creating a new app.
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<code-example path="ngmodules/src/app/app.module.1.ts" header="src/app/app.module.ts (default AppModule)" linenums="false"> // @NgModule decorator with its metadata
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</code-example>
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At the top are the import statements. The next section is where you configure the `@NgModule` by stating what components and directives belong to it (`declarations`) as well as which other modules it uses (`imports`). For more information on the structure of an `@NgModule`, be sure to read [Bootstrapping](guide/bootstrapping).
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<hr />
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## More on NgModules
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You may also be interested in the following:
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* [Feature Modules](guide/feature-modules).
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* [Entry Components](guide/entry-components).
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* [Providers](guide/providers).
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* [Types of NgModules](guide/module-types).
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