UICollectionView snap cell vertically

UICollectionViewFlowLayout.m

- (CGPoint)targetContentOffsetForProposedContentOffset:(CGPoint)proposedContentOffset withScrollingVelocity:(CGPoint)velocity {
    CGPoint contentOffset = CGPointZero;
    NSInteger itemHeight = 130;
    NSInteger padding = 10;

    NSInteger index = round(proposedContentOffset.y / (itemHeight + padding));
    NSInteger x = (itemHeight + padding) * index;
    contentOffset = CGPointMake(proposedContentOffset.x, x);

    return contentOffset;
}