[Angular] Angular Custom Change Detection with ChangeDetectorRef

Each component has its own ChangeDetectorRef, and we can inject ChangeDetectorRef into constructor:

export class ChildComponent implements OnInit {

  constructor(

    private cdr: ChangeDetectorRef

  )

For example if you have a huge list can be updated in real time though some real time database.

Update in real time is really expensive for huge list.

We have build a custom change detector, for example, update every 5 seconds, to check changes, to do that, we need to two things,

1. Disable default change detector

2. Check for changes every 5 seconds.

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

import { ListService } from './list.service';

@Component({

  selector: 'app-child',

  templateUrl: './child.component.html',

  styleUrls: ['./child.component.css']

})

export class ChildComponent implements OnInit {

  constructor(

    private cdr: ChangeDetectorRef,

    private dataProvider: ListService

  ) {

    // disable default change detector

    cdr.detach();

    // now every 5second, do a check for its child tree

    setInterval(() => { this.cdr.detectChanges(); }, );

  }

  ngOnInit() {

  }

}

There is another API: reattach() which uses for reset to default Angular change dectctor.

巴特西

[Angular] Angular Custom Change Detection with ChangeDetectorRef

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