检测由父角度2触发的子组件变量的变化

Question

我有2个文件.app.ts和Child.ts

我正在从app向子节点发送变量,我想检测变量中的任何变化并相应地显示数据.我无法检测到变量的变化.

任何帮助？我附上了Plunker Link,我还在评论中解释了我想在Child.ts文件中做什么

App.ts文件

//our root app component
import {Component, NgModule} from '@angular/core'
import {BrowserModule} from '@angular/platform-browser'
import {ChildCom} from './child.ts'

@Component({
    selector: 'my-app',
    template: `
    <div>
        <h2>Hello</h2>
        <child-com newdata={{data}}></child-com>
    </div>
    `,
})
export class App {
    data: any = [];

      constructor(){
          this.data = [{"name":"control","status":"false"}];
    }
}

@NgModule({
    imports: [ BrowserModule ],
    declarations: [ App, ChildCom ],
    bootstrap: [ App ]
})
export class AppModule {}

Child.ts文件

import {Component, Input} from '@angular/core';

@Component({
  selector: 'child-com',
  template: `
    <div>
      <p>Controls: {{newdata}}</p>
    </div>
  `,
})

export class ChildCom {
  @Input() newdata: any = [];

  constructor(){
  }

  // here I want to check if value of control in newdata variable is false 
  // then display message on front end "your controls are not working"
  // if value of control in newdata variable is true
  // then display message on front end "your controls are working fine."
  // this should automatically happen whenever I change the value of newdata variable
}

Plunker Link

Answer 1

要么你做newData一个制定者,要么你实施OnChanges

export class ChildCom {
  private _newdata: any = [];
  @Input() 
  set newdata(value) {
    // code here
  }
}

export class ChildCom implements OnChanges {
  @Input() set newdata(: any = [];

  ngOnChanges(changes) {
    // code here
  }
}

https://angular.io/docs/ts/latest/api/core/index/OnChanges-class.html

暗示

newdata={{data}}

很好,但只支持字符串值

[newdata]=data

支持所有类型的值.

这是一个更新的plnkr的链接来解释相同的,https: //plnkr.co/edit/5ahxWJ？p = preview