如何订阅一次事件发射器？

Question

// Part of service
public someEvent: EventEmitter<number> = new EventEmitter();

....

// Component
@Component({
  selector: 'some-component',
  template: `...`
})
export class SomeComponent {
  constructor(public service: Service) {
    this.service.someEvent.subscribe((x) => {
      // Do something
    });
  }
}

SomeComponent在/路线中显示.当我在我的应用程序中导航到不同的路径并再次返回时,SomeComponent将再次订阅该事件,导致回调触发两次.如何订阅一次事件或取消订阅组件的破坏并再次订阅？

// Can't subscribe after.
ngOnDestroy() {
  this.service.someEvent.unsubscribe();
}

Answer 1

一个调用subscribe返回一个实例Disposable,它有一个方法dispose.

或者,如果您使用的是RxJS 5,dispose则已重命名为unsubscribe(感谢@EricMartinez).

并从RxJS文档:

...当我们不再有兴趣接收数据时,我们会在订阅时调用dispose.

存储您的通话结果,subscribe然后在其中处理订阅ngOnDestroy.

RxJS 5:

export class SomeComponent {
  constructor (public service: Service) {
    this.subscription = this.service.someEvent.subscribe((x) => {...});
  }
  ngOnDestroy () {
      this.subscription.unsubscribe();
  }
}

RxJS <5:

export class SomeComponent {
  constructor (public service: Service) {
    this.subscription = this.service.someEvent.subscribe((x) => {...});
  }
  ngOnDestroy () {
      this.subscription.dispose();
  }
}