组件无法订阅数据源 [英] Component cannot subscribe to data source

问题描述

我让这个组件监听来自服务的消息.请注意，下面显示的每个 console.log() 语句至少被命中一次，所有内容都会被记录. 也就是说，除了向数组添加消息"之外 - 不会被记录，但应该被记录！

I have this component listening for messages from a service. Note that every console.log() statement shown below is hit at least once, everything gets logged. That is, except "adding message to array" - that does not get logged, but it should get logged!

这是组件:

import {Component, OnInit, Inject} from '@angular/core';
import {ChromeDataService} from '../../../../shared/services/events';


@Component({
  providers: [ChromeDataService],
  selector: 'app-events-list',
  templateUrl: './events-list.component.html',
  styleUrls: ['./events-list.component.scss']
})

export class EventsListComponent implements OnInit {

  isShowEventsList = false;
  events = [];

  constructor(private data: ChromeDataService) {
       console.log('events list component is constructed.');
  }

  ngOnInit() {
    console.log('events list component ngOnInit called.');
    this.data.currentMessage.subscribe(message => {
      console.log('adding message to array: ', message);
      this.events.push(message);
    })
  }

  showEventsList() {
    this.isShowEventsList = true;
  }

  hideEventsList() {
    this.isShowEventsList = false;
  }

}

这是数据源(Angular 服务):

here is the data source (an Angular service):

///<reference types="chrome"/>

import {Injectable, Component, Inject} from '@angular/core';
import {ReplaySubject} from "rxjs/ReplaySubject";

@Injectable()
export class ChromeDataService {

  private messageSource = new ReplaySubject<Object>();
  public currentMessage = this.messageSource.asObservable();
  private isListening: boolean = false;
  private listener: any;

  constructor() {

    const self = this;
    this.listener = function (msg, sender, sendResponse) {
      const parsed = JSON.parse(msg);
      console.log('extension received a message:', parsed);
      self.changeMessage(parsed);
    };
  }

  changeMessage(message: Object) {
    this.messageSource.next(message);
  }

  stopListening() {
    this.isListening = false;
    chrome.runtime.onMessage.removeListener(this.listener);
  }

  startListening() {
    this.isListening = true;
    chrome.runtime.onMessage.addListener(this.listener);
  }


}

有谁知道为什么当 changeMes​​sage() 被调用时，subscribe() 回调没有被调用?

does anyone know why when changeMessage() is called, that the subscribe() callback does not get invoked?

一个重要提示是，当我使用 new BehaviorSubject