如何在Angular 4中将数据从父组件传递到子组件

Question

当我尝试将数据从父组件传递到子组件时.我在控制台中收到未定义的消息.数据采用数组的形式.

parent.component.html

<div class="section welcome-section fp-section fp-table" *ngFor="let section of sections">
    <div class="fp-tableCell">
      <app-question-card [data]="section"></app-question-card>
    </div>
  </div>

child.component.ts

@Input() data;
  question = [];
  constructor() {
    this.question = this.data;
  }

  ngOnInit() {
    console.log(this.question); //returns undefined
  }

Answer 1

你不能在构造函数中进行赋值,因为尚未填充值,它应该ngOnInit像检查值一样完成.

@Input() data;
question = [];

constructor() {
}

ngOnInit() {
  this.question = this.data;
  console.log(this.question);
}