Angular 7通过两次调用的服务订阅方法通信

import { Injectable } from '@angular/core';
import { Subject } from 'rxjs';

@Injectable({
  providedIn: 'root'
})
export class DataService {
  private dataSubject = new Subject<any>();

  sendData(data: any) {
    this.dataSubject.next(data);
  }

  getData() {
    return this.dataSubject.asObservable();
  }
}

import { Component } from '@angular/core';
import { DataService } from './data.service';

@Component({
  selector: 'app-sender',
  template: `
    <button (click)="sendData()">Send Data</button>
  `
})
export class SenderComponent {
  constructor(private dataService: DataService) {}

  sendData() {
    this.dataService.sendData('Hello from Sender');
  }
}

import { Component } from '@angular/core';
import { DataService } from './data.service';

@Component({
  selector: 'app-receiver',
  template: `
    <div>{{ receivedData }}</div>
  `
})
export class ReceiverComponent {
  receivedData: string;

  constructor(private dataService: DataService) {
    this.dataService.getData().subscribe(data => {
      this.receivedData = data;
    });
  }
}