UIScrollView delegate methods not calling properly

Question

In order to scroll up and down i need to call two methods for that I have used the below method .I am using scrollview delegate method for UICollection as it is the subview for UIScrollView.Here is the code that I have written but the scroll is not easily moving and the result is also not accurate for some times can any one suggest.?

- (void)scrollViewWillBeginDecelerating:(UIScrollView *)scrollView{
    CGPoint mScrollPosition = [scrollView.panGestureRecognizer velocityInView:mCollectionView];


    if (mScrollPosition.y > 0.0f){
        NSLog(@"going down");
       //Action One
        mYearHeaderTitle--;
        [self.mCollectionView reloadData];

    }
    else if (mScrollPosition.y < 0.0f){
        NSLog(@"going up");
      //Action two
        mYearHeaderTitle++;
        [self.mCollectionView reloadData];
    }
}

Answer 1

Use :

1. - (void)scrollViewDidScroll:(UIScrollView *)scrollView
2. - (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView

Instead :

- (void)scrollViewWillBeginDecelerating:(UIScrollView *)scrollView