为什么更改NgOninit上的父级数据不会导致ExpressionChangedAfterItHaHasBeenCheckedError？

Question

Under this example

parentComponent {
  text = 'dsfsdf';
}

childComponent implements Oninit {
    @Input() text;
   ngOnInit() {
     this.text = 'something else';
    }
}

why does this not cause ExpressionChangedAfterItHasBeenCheckedError please? And what is a simple way of getting this error to occur?

Answer 1

This won't trigger an ExpressionChangedAfterItHasBeenCheckedError because changing the value of an @Input parameter does not trigger any event to the parent and so it just doesn't re-render at all.

A simple way to make this error occur:

<div>{{functionThatReturnsDifferentValueOnEveryCall()}}</div>

...

count = 0;

functionThatReturnsDifferentValueOnEveryCall() {
   return count++;
}