RxJs主题错误-无法读取未定义的属性“订阅" [英] RxJs Subject error - cannot read property 'subscribe' of undefined

问题描述

在返回Observable的服务方法中，我试图通过Subject通知组件操作已完成.

In my service method that returns Observable I'm trying to notify the component via Subject that an action completed.

completed: Subject<boolean>

  constructor(private http: Http) {

  }

  loadItems(): Observable<FrontItemDto[]> {
    return this.http.get ( `${ServiceSettings.ApiUrl}/front` )
      .map ( res => {
        res.json ();
        if ( res.json () ) {
          this.completed.next ( true );
        }
      } )
      .catch ( (error: any) => Observable.throw ( error.json ().error || 'Server error' ) );
  }

这是组件监听Subject的方式:

ngOnInit(): void {
    this.getItems();
    this.sub = this.dataService.completed.subscribe(completed => {
      if (completed) {
        this.show = false;
      }
      });
  }

但是我收到一条错误消息，指出未定义主题(已完成).我在做什么错了?

But I'm getting an error saying that Subject (completed) is undefined. What am I doing wrong?

推荐答案

您尚未正确初始化completed主题

completed = new Subject<boolean>(); //it should have parenthesis at the end

演示 (@Ompurdy)

Demo by @Ompurdy

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