If you think ngDoCheck means your component is being checked — read this article

[maxkoretskyi]

In this article I'll explain in great detail when is ngDoCheck triggered which will make it clear why ngDoCheck lifecycle hook is still triggered for a component that implements OnPush change detection strategy.

Read the article here.

[otec-valerian]

Thanks a lot for the article! But I`m interested in whether its possible to change this:

ngOnChanges() {
this.id = this.o.id;
}

ngDoCheck() {
if (this.id !== this.o.id) {
this.cd.markForCheck();
}
}

To this:

ngOnChanges(changes: SimpleChanges) {
if (changes.o){
this.cd.markForCheck();
}
}

ngDoCheck() {
}

Just simply remove ngDoCheck and check object mutation just in ngOnChanges ?
How I understand ngDoCheck have to be used in the cases of OWN objects (not @input ones) mutation. Because it seems to be cleaner to use ngOnChanges for the @input objects mutations track how I mentioned before.

[lethiandev]

It won't work, and it's redundant to markForCheck when it's already being checked, but as for the example, since you don't update the o's input binding, the second ngOnChanges lifecycle won't be triggered as it depends on checking the o's input by reference. That's why ngDoCheck triggers the ngOnChanges lifecycle when the o's property changed (mutated), not the other way.