一、我们要实现的效果

效果图.png

1是根组件，当组件7想把消息传递给组件8时，我们这时就需要中间人组件3

如果你已经看了我的上一篇博客《Angular输入输出属性》这篇文章会更好理解，没有的话也完全ok

二、代码示例

新建2个组件product、price

ng g product
ng g price

1.price组件

//price.component.html
<div style="border-top: 1px solid #000">
  <h2>这里是价格组件</h2>
  <div>
    商品id:{{id}}
    商品价格：{{price|number:'2.2-2'}}
  </div>
  <button (click)="buyNow($event)">立即购买</button>
</div>
//price.component.ts
import {Component, EventEmitter, OnInit, Output} from '@angular/core';

@Component({
  selector: 'app-price',
  templateUrl: './price.component.html',
  styleUrls: ['./price.component.css']
})
export class PriceComponent implements OnInit {
  id: string = 'product1';
  price: number;
  @Output()
  buy: EventEmitter<PriceRandom> = new EventEmitter();

//EventEmitter后面的<PriceRandom>这个范型代表的是发射出去值的类型，这里是PriceRandom
  constructor() {
    setInterval(() => {
      let priceRandom: PriceRandom = new PriceRandom(this.id, 100 * Math.random());
      this.price = priceRandom.lastPrice;
    }, 2000);
  }

  ngOnInit() {
  }

  buyNow(event) {
    this.buy.emit(new PriceRandom(this.id, this.price));
  }

}

export class PriceRandom {
  constructor(public id: string,
              public lastPrice: number) {
  }
}

2.根组件（中间人）

//app.component.html
<h1>
  我是主组件
</h1>
<!--价格组件 start-->
<app-price (buy)="buyHandle($event)"></app-price>
<!--价格组件 end-->
<!--订单组件 start-->
<app-order [nowPrice]="price"></app-order>
<!--订单组件 end-->
//app.component.ts
import {Component} from '@angular/core';
import {PriceRandom} from './price/price.component';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  price: PriceRandom = new PriceRandom('', 0);

  buyHandle(event: PriceRandom) {
    this.price = event;
  }
}

3.order组件

//order.component.html
<h2>
  我是订单组件
</h2>
<h4>
  点击购买时的商品价格为：{{nowPrice.lastPrice}}
</h4>
//order.component.ts
import {Component, Input, OnInit} from '@angular/core';
import {PriceRandom} from '../price/price.component';

@Component({
  selector: 'app-order',
  templateUrl: './order.component.html',
  styleUrls: ['./order.component.css']
})
export class OrderComponent implements OnInit {
  @Input()
  nowPrice: PriceRandom;

  constructor() {
  }

  ngOnInit() {
  }

}

4.效果

效果.png