如何从一个服务抛出错误并在Angular2的另一个组件中捕获它

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

@Injectable()
export class MyService {
  private errorSubject: Subject<string> = new Subject<string>();

  throwError(errorMessage: string) {
    this.errorSubject.next(errorMessage);
  }

  getErrorSubject() {
    return this.errorSubject.asObservable();
  }
}

import { Component, OnDestroy } from '@angular/core';
import { Subscription } from 'rxjs';
import { MyService } from './my.service';

@Component({
  selector: 'app-my-component',
  template: `
    <div>{{ errorMessage }}</div>
  `,
})
export class MyComponent implements OnDestroy {
  errorMessage: string;
  private errorSubscription: Subscription;

  constructor(private myService: MyService) {
    this.errorSubscription = this.myService.getErrorSubject().subscribe(
      (errorMessage: string) => {
        this.errorMessage = errorMessage;
      }
    );
  }

  ngOnDestroy() {
    this.errorSubscription.unsubscribe();
  }
}