我是 Angular 7 的新手，我想知道我是否走在正確的道路上。我有一個(gè)“警報(bào)”組件，它只在頂部的頁(yè)面上顯示一個(gè) boostrap 警報(bào)框。我希望能夠調(diào)用此警報(bào)并從任何組件顯示它。我很確定我需要一個(gè)服務(wù)，我可以調(diào)用它來傳遞消息，然后讓警報(bào)組件訂閱該服務(wù)以偵聽傳入的消息？到目前為止，我可以調(diào)用該服務(wù)并向其傳遞一條“消息”，我只是不知道如何在警報(bào)組件中訂閱/收聽（我認(rèn)為這是正確的術(shù)語(yǔ)）以偵聽要顯示的傳入消息。前任。登錄組件constructor(public authService: AuthService, private router: Router, private alert: AlertService) {}login() {  this.authService.login(this.model).subscribe(next => {    this.alert.success('Logged in successfully');  }, error => {    this.alert.failure('Log in failed');  }, () => {    // do something else  });}然后這是我的服務(wù)前任。警報(bào)服務(wù)import {  Injectable} from '@angular/core';@Injectable({  providedIn: 'root'})export class AlertService {  constructor() {}  success(message: string) {  // do something here?  }  error(message: string) {  // do something here?  }}然后我有我的 AlertComponent，但不確定我將如何訂閱/監(jiān)聽從 AlertService 顯示的傳入消息。前任。警報(bào)組件.tsexport class AlertComponent implements OnInit {  dismissible = true;  alerts: any[];  constructor() { }  ngOnInit() {    this.add();  }  // do something here to subscribe/listen to incoming messages from the service??  add(): void {    this.alerts.push({      type: 'info',      msg: `This alert will be closed in 5 seconds (added: ${new Date().toLocaleTimeString()})`,      timeout: 5000    });  } }和 html<div *ngFor="let alert of alerts">  <alert [type]="alert.type" [dismissible]="dismissible" [dismissOnTimeout]="alert.timeout">{{ alert.msg }}</alert></div>