Question

是否有可能只检测angular2中特定绑定属性的更改？

 export class Test{
     @Input() a;
     @Input() b;
     constructor() {
         }

     ngOnChanges(){
         //I want that this only called when a changed
         console.log(this.a);
     }
}

Answer 1

正如Eric所说，ngOnChanges的每次更新都会调用@Input方法。

如果您只想检测@Input“a”的更新，您可以使用setter：

export class SubComponent {
  @Input()
  set a(a:string) {
    this._a = a;
    console.log('a updated');
  }

  @Input()
  b:any;

  (...)
}

请参阅此plunkr：https://plnkr.co/edit/UKyRiq?p=preview。

Answer 2

使用，（您将在agrs 中获得两个变量值）

ngOnChanges(...args: any[]) {  
        console.log('onChange fired');
        console.log('changing', args); // so can access both variables here in args.
        console.log('changing', args[0]); //a's current and previous value if i'm not wrong.
        console.log('changing', args[1]); //b's current and previous value if i'm not wrong.
 }

Answer 3

ngOnChanges(changes: SimpleChanges): void {
    if ('a' in changes) {
        // do your thing
    }
}

Angular 2 ngOnChanges仅用于特定绑定

3 个答案: