Why does Angular 2 not detect change?

Question

I am having a similar code and error as Expression ___ has changed after it was checked where I am changing a variable value in ngAfterViewInit().

One of the answers https://stackoverflow.com/a/35243106/1460595 suggests to manually trigger change detection by calling detectChanges() method of ChangeDetectorRef, which works.

But why do we have to handle change manually when Angular 2 should be handling the change?
Is there some relationship between lifecycle hooks and change detection?

score 0 · Answer 1 · answered Feb 08 '17 at 14:43

0

The problem is caused by a 2nd change detection run after each regular one done by Angular in development mode, to check if the model has stabilized, otherwise this is an indication for a probable bug.

In your case the problem is, that the lifecycle callback ngAfterViewInit is called by the first change detection run. If it updates the modelm the 2nd change detection run throws. With a manual change detection run after the update, Angular gets its remembered values updates and the 2nd CD run won't notify a change.

answered Feb 08 '17 at 14:43

Günter Zöchbauer

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so is there a lifecycle hook that tells us change detection run is complete? – Flake Feb 08 '17 at 15:14
No, just run `detectChanges()`. I haven't seen a better method yet. You could try `ngAfterContentInit`, don't remember if you get the error as well. – Günter Zöchbauer Feb 08 '17 at 15:24

Why does Angular 2 not detect change?

1 Answers1