Question

我有一个简单的自定义指令，带有输入，我在我的组件中绑定。但无论出于何种原因，在更改输入属性的子属性时，ngOnchanges（）方法都不会触发。

my.component.ts

import {Component} from 'angular2/core';
import {MyDirective} from './my.directive';

@Component({
    directives: [MyDirective],
    selector: 'my-component', 
    templateUrl: 'Template.html'
})

export class MyComponent {
    test: { one: string; } = { one: "1" }

    constructor( ) {
        this.test.one = "2";
    }
    clicked() {
        console.log("clicked");
        var test2: { one: string; } = { one :"3" };
        this.test = test2; // THIS WORKS - because I'm changing the entire object
        this.test.one = "4"; //THIS DOES NOT WORK - ngOnChanges is NOT fired=
    }
}

my.directive.ts

import {Directive, Input} from 'angular2/core';
import {OnChanges} from 'angular2/core';

@Directive({
    selector: '[my-directive]',
    inputs: ['test']
})

export class MyDirective implements OnChanges {
    test: { one: string; } = { one: "" }

    constructor() { }

    ngOnChanges(value) {
        console.log(value);
    }
}

template.html

<div (click)="clicked()"> Click to change </div>
<div my-directive [(test)]="test">

谁能告诉我为什么？

Answer 1

事实上，这是一种正常的行为，Angular2不支持深度比较。它仅基于参考比较。请参阅此问题：https://github.com/angular/angular/issues/6458。

这就是说它们是一些解决方法，通知指令对象中的某些字段已更新。

引用组件中的指令

export class AppComponent {
  test: { one: string; } = { one: '1' }
  @ViewChild(MyDirective) viewChild:MyDirective;

  clicked() {
    this.test.one = '4';
    this.viewChild.testChanged(this.test);
  }
}

在这种情况下，显式调用指令的testChanged方法。请参阅此plunkr：https://plnkr.co/edit/TvibzkWUKNxH6uGkL6mJ?p=preview。

在服务中使用事件

专用服务定义testChanged事件

export class ChangeService {
  testChanged: EventEmitter;

  constructor() {
    this.testChanged = new EventEmitter();
  }
}

该组件使用服务来触发testChanged事件：

export class AppComponent {
  constructor(service:ChangeService) {
    this.service = service;
  }

  clicked() {
    this.test.one = '4';
    this.service.testChanged.emit(this.test);
  }
}

该指令订阅此testChanged事件以便收到通知

export class MyDirective implements OnChanges,OnInit {
  @Input()
  test: { one: string; } = { one: "" }

  constructor(service:ChangeService) {
    service.testChanged.subscribe(data => {
      console.log('test object updated!');
    });
  }
}

希望它可以帮到你，亨利

Angular2子属性更改未在绑定属性上触发更新

1 个答案: