angular 4服务如何只更新选定的组件

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

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

  setSelectedComponent(component: string) {
    this.selectedComponent.next(component);
  }

  getSelectedComponent() {
    return this.selectedComponent.asObservable();
  }
}

import { Component, OnInit } from '@angular/core';
import { MyService } from 'path-to-my-service';

@Component({
  selector: 'app-my-component',
  templateUrl: './my-component.component.html',
  styleUrls: ['./my-component.component.css']
})
export class MyComponent implements OnInit {
  selectedComponent: string;

  constructor(private myService: MyService) { }

  ngOnInit() {
    this.myService.getSelectedComponent().subscribe(component => {
      this.selectedComponent = component;
      // 执行更新组件的逻辑
    });
  }
}

import { Component } from '@angular/core';
import { MyService } from 'path-to-my-service';

@Component({
  selector: 'app-another-component',
  templateUrl: './another-component.component.html',
  styleUrls: ['./another-component.component.css']
})
export class AnotherComponent {
  constructor(private myService: MyService) { }

  updateSelectedComponent(component: string) {
    this.myService.setSelectedComponent(component);
  }
}