Observable do not receive the next value in angular2

问题

In order to pass value between angular2 different components, I use different services injected into different components.

In my PagesService component, I define a behavior subject and want to pass a value.

import { Injectable } from '@angular/core';
import { ApiService } from '../../apiService/api.service';
import { Playlists } from '../shared/playlists.model';
import { Subject, BehaviorSubject } from 'rxjs/Rx';


@Injectable()
export class PagesService {

  private currentPlaylists: Subject<Playlists> = new BehaviorSubject<Playlists>(new Playlists());

  constructor(private service: ApiService) {

  }

  getCurrentPlaylists() {
    return this.currentPlaylists.asObservable();
  }

  setCurrentPlaylists(playlists: Playlists) {
    console.log(playlists, 'i am here');
    this.currentPlaylists.next(playlists);
  }
}

I need to pass the playlists to a component called PagesComponent

 import { Component, OnInit, Input, Output, OnChanges, EventEmitter, Injectable } from '@angular/core';
    import { Http, Response } from '@angular/http';
    import { Observable } from 'rxjs/Observable';
    import { PagesService } from './shared/pages.service';
    import { Subject,BehaviorSubject } from 'rxjs/Rx';
@Component({
  selector: 'pages',
  styleUrls: ['app/pages/pages.css'],
  templateUrl: 'app/pages/pages.html',
  providers: [PagesService]
})
            export class PagesComponent {

              playlists: Playlists;

              constructor(private service: PagesService, private playlistService: PlaylistService) {
                this.playlists = new Playlists();
                this.service.getCurrentPlaylists().subscribe((playlists) => {
                  console.log(playlists, 'new playlists coming');
                  this.playlists = playlists;
                }, error => {
                  console.log(error);
                });
              }
        }

This is the console output:

After I update the playlists, you can see the actual playlists I want to pass printed out to the console, but I do not receive it in pages component,

Any ideas?

Thanks

回答1:

Which component is calling setCurrentPlaylists()?

Most likely, some component other than PagesComponent is calling this method and that other component probably has providers: [PagesService] defined in its metadata. This will result in two instances of PagesService being created – one that PagesComponent provides (and injects), and another instance that some other component provides (and injects).

来源：https://stackoverflow.com/questions/38906315/observable-do-not-receive-the-next-value-in-angular2