将变量从一个组件中的服务访问到Angular 7中的另一个组件

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

@Injectable({
  providedIn: 'root'
})
export class DataService {
  private sharedData = new BehaviorSubject<string>('');

  setData(data: string) {
    this.sharedData.next(data);
  }

  getData() {
    return this.sharedData.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() {
    const data = 'Hello from SenderComponent';
    this.dataService.setData(data);
  }
}

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

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

  constructor(private dataService: DataService) {}

  ngOnInit() {
    this.dataService.getData().subscribe(data => {
      this.receivedData = data;
    });
  }
}