【Angular】Angula6中的组件通信

<app-child childTitle="可设置子组件标题"></app-child>

import { Component, OnInit, Input } from '@angular/core';
@Input childTitle: string;

<app-child #child></app-child> <button (click)="child.childPrint()"></button>

childPrint() {
  alert("来自子组件的打印");
}

import { Component, OnInit, Output, EventEmitter } from '@angular/core';
...
@Output() initEmit = new EventEmitter<string>();
ngOnInit() {
  this.initEmit.emit("子组件初始化成功");
}
...

<app-child (initEmit)="accept($event)"></app-child>

accept(msg:string) {
  alert(msg);
}

sendInfo() {
  return 'Message from child 1.';
}

<button (click)="getInfo()">获取子组件1号的信息</button>
<h2>{{ info }}</h2>

import { Component, OnInit, ViewChild } from '@angular/core';
...
@ViewChild(ChildFirstComponent) private childcomponent: ChildFirstComponent;
getInfo() {
  this.info = this.childcomponent.sendInfo();
}

import { Component, Injectable, EventEmitter } from "@angular/core";
@Injectable()
export class myService {
  public info: string = "";
  constructor() {}
}

import { myService } from '../../service/myService.service';
...
constructor(
  public service: myService
) { }

changeInfo() {
  this.service.info = this.service.info + "1234";
}
...

import { myService } from '../../service/myService.service';
...
constructor(
  public service: myService
) { }

showInfo() {
  alert(this.service.info);
}
...

import { BehaviorSubject } from 'rxjs';
...
public messageSource = new BehaviorSubject<string>('Start');
changemessage(message: string): void {
  this.messageSource.next(message);
}

changeInfo() {
  this.communication.changemessage('Message from child 1.');
}
ngOnInit() {
  this.communication.messageSource.subscribe(Message => {
    window.alert(Message);
    this.info = Message;
  });
}