（一）Angular5 高级教程--基于 RxJS Subject的组件间通信

message.service.ts

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

@Injectable()
export class MessageService {
private subject = new Subject<any>();

sendMessage(message: string) {
this.subject.next({ text: message });
}

clearMessage() {
this.subject.next();
}

getMessage(): Observable<any> {
return this.subject.asObservable();
}
}

home.component.ts

import { Component } from '@angular/core';
import { MessageService } from './message.service';

@Component({
selector: 'exe-home',
template: `
<div>
<h1>Home</h1>
<button (click)="sendMessage()">Send Message</button>
<button (click)="clearMessage()">Clear Message</button>
</div>`
})

export class HomeComponent {
constructor(private messageService: MessageService) {}

sendMessage(): void {
this.messageService.sendMessage('Message from Home Component to App Component!');
}

clearMessage(): void {
this.messageService.clearMessage();
}
}

app.component.ts

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

@Component({
selector: 'my-app',
template: `
<div>
<div *ngIf="message">{{message.text}}</div>
<exe-home></exe-home>
</div>
`
})

export class AppComponent implements OnDestroy {
message: any;
subscription: Subscription;

constructor(private messageService: MessageService) {
this.subscription = this.messageService
.getMessage().subscribe( message => {
this.message = message;
});
}

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