title: Scroll UICollectionView to section header view
body: <p>The code below scrolls to the right cell in <code>UICollectionView</code>, but the section header view is hidden behind <code>UINavigationBar</code> in my case. I believe I should use <code>scrollRectToVisible</code> instead and my question is, what is the right way to calculate the <code>CGRect</code> (y position) when the <code>numberOfRows</code> in a given <code>section</code> is variable.</p>
  
  <pre><code>- (void)scrollToPricing:(NSUInteger)row {
  
      [self.collectionView scrollToItemAtIndexPath:
        [NSIndexPath indexPathForItem:0 
                            inSection:row] 
                     atScrollPosition:UICollectionViewScrollPositionTop 
                             animated:YES];
  }
  </code></pre>