UIScrollView scrollRectToVisible:animated: is there a way that a method can be called when animation ends

Yup use scrollViewDidEndScrollingAnimation

I do it like this because sometimes using the delegate isn't practical for me, like if i'm doing it in UIViewController transition:

[UIView animateWithDuration:0.3 animations:^{
    [scrollView setContentOffset:CGPointMake(0, -scrollView.contentInset.top) animated:NO];
} completion:^(BOOL finished) {
    // This is called when it's complete
}];

Implement UIScrollViewDelegate delegate methods for your UIScrollView the following way:

Use scrollViewDidEndScrollingAnimation: to detect when the scrolling animation concludes when you've initiated the scrolling by calling setContentOffset:animated: or scrollRectToVisible:animated: methods (with animated:YES).

If you want to monitor scroll view motion that's been initiated by touch gestures, use scrollViewDidEndDecelerating: method, which is called when the scrolling movement comes to a halt.