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Injectable

标记性元数据，表示一个类可以由 Injector 进行创建。

Decorator that marks a class as available to be provided and injected as a dependency.

选项说明
providedIn

Determines which injectors will provide the injectable, by either associating it with an @NgModule or other InjectorType, or by specifying that this injectable should be provided in one of the following injectors:

  • 'root' : The application-level injector in most apps.
  • 'platform' : A special singleton platform injector shared by all applications on the page.
  • 'any' : Provides a unique instance in every module (including lazy modules) that injects the token.

参见

选项

providedIn

Determines which injectors will provide the injectable, by either associating it with an @NgModule or other InjectorType, or by specifying that this injectable should be provided in one of the following injectors:

  • 'root' : The application-level injector in most apps.
  • 'platform' : A special singleton platform injector shared by all applications on the page.
  • 'any' : Provides a unique instance in every module (including lazy modules) that injects the token.
providedIn: Type<any> | 'root' | 'platform' | 'any' | null
      
      providedIn: Type<any> | 'root' | 'platform' | 'any' | null

使用说明

Marking a class with @Injectable ensures that the compiler will generate the necessary metadata to create the class's dependencies when the class is injected.

下面的例子展示了如何正确的把服务类标记为可注入的（Injectable）。

The following example shows how a service class is properly marked so that a supporting service can be injected upon creation.

@Injectable() class UsefulService { } @Injectable() class NeedsService { constructor(public service: UsefulService) {} } const injector = Injector.create({ providers: [{provide: NeedsService, deps: [UsefulService]}, {provide: UsefulService, deps: []}] }); expect(injector.get(NeedsService).service instanceof UsefulService).toBe(true);
      
      @Injectable()
class UsefulService {
}

@Injectable()
class NeedsService {
  constructor(public service: UsefulService) {}
}

const injector = Injector.create({
  providers:
      [{provide: NeedsService, deps: [UsefulService]}, {provide: UsefulService, deps: []}]
});
expect(injector.get(NeedsService).service instanceof UsefulService).toBe(true);