当 Observable/subscrption 更改属性时，ngOnChanges 不会触发

问题描述

我正在尝试在 Observable/subscribe 完成后做一些事情.我正在更改 subscribe( onNext ) 方法中的 Input 属性，但 ngOnChanges 永远不会触发.

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

那是按设计"

ngOnChanges() 仅在更改检测更新与 @Input() 的绑定时调用.如果从某处强制更改输入，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.

只需让 names 成为每次更新属性时执行的代码的 getter/setter.

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

这篇关于当 Observable/subscrption 更改属性时，ngOnChanges 不会触发的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！