参考：https://www.cnblogs.com/fuzitu/p/9172728.html

https://www.it1352.com/1551144.html

通过输入和输出属性 实现数据在父子组件的交互
在子组件内部使用@input接受父组件传入数据，使用@output传出数据到父组件
详细标准讲解参考官方文档
https://angular.cn/guide/component-interaction#pass-data-from-parent-to-child-with-input-binding

但是我在开发中遇到这样一个问题，当父组件传入的数据是在网络请求回来之后才被赋值，这时的子组件已经初始化结束，就会存在异步的问题
解决办法是使用ngOnChanges()来截听输入属性值的变化，然后在自己的代码里处理数据;

代码如下：
父组件使用子组件代码 parent传入child传出

父：

<child-app [parent]="parent" (child)="getChild($event)"></child-app>

父：

getChild(child) {//子组件返回数据console.log(child)
}

子：
 

@Component({selector: 'child-appt',templateUrl: './app.component.html',styleUrls: ['./app.component.scss']
})@Input() parent: any;
@Output() child = new EventEmitter<any>()ngOnChanges(changes: SimpleChanges): void {if (changes['parent'] !== undefined) {this.curParent = changes['parent'].currentValue;}
}this.child.emit(data);

另一个答案：

I have a child component that contains complex input (some chart data). I am sending this chart data from the parent component through the @Input() decorator in Angular 5 after getting API response. So, I need to sync the chart according with the API response every time it gets changed on the parent component, hence, the OnChange Lifecyle. But unfortunately, I am not able to get this to work properly. I tried with setting a dummy input field with basic number type and increment it but in vain. Here's my implementation:

Child chart component:

export class ChartComponent implements OnInit, OnChanges {@Input() chartData;@Input() triggerChart;ngOnChanges(changes: SimpleChanges) {console.log(changes);}}

Parent component html:

<app-chart [chartData]="chartData" [triggerChart]="triggerChartData"></app-chart>
<input [(ngModel)]="triggerChartData" type="hidden">

Parent component:

this.chartService.getChartData(params).subscribe(res => {this.chartData = res;this.triggerChartData++;
});