当我重新访问页面时订阅会触发两次

Question

我遇到了 subscribe 触发 2 次的场景。但是，如果我通过将轮询器方法复制粘贴到我的组件中来摆脱该服务，那么问题就会消失。

我正在 Ionic 3 中运行，但我认为这在这里并不重要。“rxjs”：“5.4.3”

unsubscribe()被召唤ngDestroy()

我的服务.service.ts

public pollingDataReceived = new Subject<any>();

pollForData = (id: string) : Subscription => {
    let stopPollingForStatus = false;
    return Observable.interval(environment['pollingInterval'])
          .takeWhile(() => !stopPollingForStatus)
          .concatMap(() => {
            return this.getAnalysisById(id);
          })
          .subscribe((analysisData) => {
            if (analysisData) {
              if (analysisData.status === 'questions') {
                stopPollingForStatus = false;
              }
              else {
                stopPollingForStatus = true;
                const result = {
                  someData: 'whatever'
                };
                console.log('raise pollingDataReceived event');// This happens ONCE
                this.pollingDataReceived.next(result);
              }
            }
            else {
              alert('no analysis data!');
            }
          });
  }

my.component.ts（订阅者）

  private pollingData: Subscription;

  someEventHandler() {
    this.pollingData = this.pollForData(this.id);
  }

  ngOnInit(): void {
    this.myService.pollingDataReceived.subscribe((data) => {
        this.analysis = data.analysisData;
        //This is getting called 2x.  Maybe I double subscribed?
        myNavigator.navigateToPageByStatus(myPage);
    }, (err) => { console.log(err); });
    }

  ngOnDestroy() {
    console.log('ngOnDestroy: unsubscribe pollingData in flow');// This does get called
    this.pollingData.unsubscribe();
  }

Answer 1

我遇到了类似的问题，请尝试下面的代码，这只是根本问题的解决方法。

this.pollingDataReceived.next(result);
this.pollingDataReceived = new BehaviorSubject<any>(); // Here, create new object with null value