Change detection does not trigger when the formgroup values change

Question

I have created a simple example to demonstrate a weird issue I\'m facing.

Stackblitz - https://stackblitz.com/edit/angular-change-detection-form-group

I hav

Answer 1

Angular only detects changes if the memory address of the variable changes. Setting the value does not change memory address, thus does not hit ngOnChanges.

Same goes with arrays. A simple push does not hit ngOnChanges, have to change memory address by = to new array.

Try this:

import { Component, Input, OnInit, OnChanges, ChangeDetectionStrategy } from '@angular/core';
import { FormGroup } from '@angular/forms';

@Component({
  selector: 'app-input',
  template: `
  

      Name :  {{form.value.name}} 


      Age :  {{form.value.age}}
  
`,
  styles: [``],
  changeDetection: ChangeDetectionStrategy.OnPush
})
export class InputComponent implements OnInit, OnChanges {
  @Input() form: FormGroup;

  ngOnInit() {
  }

  ngOnChanges(changes) {
    console.log(changes)
  }
}