Angular 4+ ngOnDestroy()在使用中-销毁可观察到的 [英] Angular 4+ ngOnDestroy() in service - destroy observable

问题描述

在有角度的应用程序中，我们为组件/指令提供了ngOnDestroy()生命周期钩子，并使用该钩子取消了对可观察对象的订阅.

In an angular application we have ngOnDestroy() lifecycle hook for a component / directive and we use this hook to unsubscribe the observables.

我想清除/破坏在@injectable()服务中创建的可观察性. 我看到一些帖子说ngOnDestroy()也可以在服务中使用.

I want to clear / destory observable that are created in an @injectable() service. I saw some posts saying that ngOnDestroy() can be used in a service as well.

但是，这是一个好习惯吗，并且是唯一的方法，何时才能调用它? 有人请澄清.

But, is it a good practice and only way to do so and When will it get called ? someone please clarify.

推荐答案

OnDestroy 生命周期挂钩是在提供程序中可用. 根据文档:

OnDestroy lifecycle hook is available in providers. According to the docs:

销毁指令，管道或服务时调用的生命周期挂钩.

Lifecycle hook that is called when a directive, pipe or service is destroyed.

这是一个示例:

@Injectable()
class Service implements OnDestroy {
  ngOnDestroy() {
    console.log('Service destroy')
  }
}

@Component({
  selector: 'foo',
  template: `foo`,
  providers: [Service]
})
export class Foo implements OnDestroy {
  constructor(service: Service) {}

  ngOnDestroy() {
    console.log('foo destroy')
  }
}

@Component({
  selector: 'my-app',
  template: `<foo *ngIf="isFoo"></foo>`,
})
export class App {
  isFoo = true;

  constructor() {
    setTimeout(() => {
        this.isFoo = false;
    }, 1000)
  }
}

请注意，在Service上面的代码中，它是属于Foo组件的一个实例，因此可以在销毁Foo时销毁它.

Notice that in the code above Service is an instance that belongs to Foo component, so it can be destroyed when Foo is destroyed.

对于属于根注入器的提供程序，这将在应用程序销毁时发生，这有助于避免使用多个引导程序(即在测试中)导致内存泄漏.

For providers that belong to root injector this will happen on application destroy, this is helpful to avoid memory leaks with multiple bootstraps, i.e. in tests.

当父注入者的提供者在子组件中被订阅时，它不会在组件销毁时被销毁，这是组件有责任在组件ngOnDestroy中退订(如另一个答案所解释).

When a provider from parent injector is subscribed in child component, it won't be destroyed on component destroy, this is component's responsibility to unsubscribe in component ngOnDestroy (as another answer explains).

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