angular4 组件间通信

父传子用@input

子传父用@output

例：子组件

<p>
    <span *ngFor="let star of stars;let i=index" class="glyphicon glyphicon-star" [class.glyphicon-star-empty]="star" (click)="clickStar(i)"></span>
    <span>{{rating | number:'1.0-2'}}星</span>  //保留两位小数
</p>

import { Component, OnInit ,Input ,Output,EventEmitter,OnChanges,SimpleChanges } from '@angular/core';

@Component({
  selector: 'app-stars',
  templateUrl: './stars.component.html',
  styleUrls: ['./stars.component.scss']
})
export class StarsComponent implements OnInit, OnChanges {

  //发生改变时，初始化星级和输入框内容
  ngOnChanges(changes: SimpleChanges):void{
    this.stars = [];
    for(let i=1;i<=5;i++){
      this.stars.push(i>this.rating)
    }
  }
//input装饰器，星级评价的组件的rating属性应该由他的父组件传递给它
  @Input()
  private rating:number = 0;

  @Output()
  private  ratingChange:EventEmitter<number> = new EventEmitter(); //这里的名字一定要用属性名+Change才能在父组件中使用[(rating)]进行双向数据绑定

  private stars:boolean[];
  @Input()
  private readonly:boolean = true;

  constructor() { }

  ngOnInit() {
      
  }

  clickStar(index:number){
    if(!this.readonly){
     this.rating = index+1;
     this.ngOnInit();
      this.ratingChange.emit(this.rating);
     }
  }

}

父组件调用子组件，进行双向数据绑定

<app-stars [(rating)]="newRating" [readonly]="false"></app-stars>