当属性由Observable/subscrption更改时，ngOnChanges不触发 [英] ngOnChanges not firing when attribute changed by Observable/subscrption

问题描述

我正在尝试在Observable/subscribe完成之后做一些事情.我正在更改subscribe( onNext )方法中的Input属性，但是ngOnChanges从不触发.

I'm trying to do something after an Observable/subscribe completes. I'm changing an Input property in the subscribe( onNext ) method, but ngOnChanges never fires.

我应该怎么做?

import { Component, EventEmitter, 
  OnInit, AfterViewInit, OnChanges, SimpleChanges,
  Input, Output
} from '@angular/core';

@Component({
  templateUrl: 'myTemplate.html'
    , providers: [ NamesService ]
})

export class MyPage  {
  @Input() names: any[];

  constructor( public namesSvc: NamesService) {}

  ngOnInit() {
    this.getNames$()
  }


  getNames$() : void {
    this.nameService.get().subscribe( 
      (result)=>{
       this.names = result;
       console.log(`getNames$, names=${this.names}`);

       // I could doSomething() here, but it doesn't seem like the correct place
       // doSomething()  

      }
      , error =>  this.errorMessage = <any>error
    )
  }

  ngOnChanges(changes: SimpleChanges) : void {
    // changes.prop contains the old and the new value...
    console.warn(`>>> ngOnChanges triggered`)
    if (changes["names"]) {
      console.warn(`>>> ngOnChanges, names=${changes["names"]}`)
      this.doSomething()
    }
  }

  doSomething(){
    console.log("doing something");
  }
}

推荐答案

这是按设计的"

ngOnChanges().如果从某处命令性地更改了输入，则不会调用它.

ngOnChanges() is only called when change detection updates a binding to an @Input(). If the input is changed imperatively from somewhere then it isn't called.

只需将names用作每次属性更新时要执行的代码的获取器/设置器即可.

Just make names a getter/setter for code to be executed every time when the property is updated.

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