title: How to determine height of UICollectionView with FlowLayout
body: <p>I've got an <code>UICollectionView</code> with an <code>UICollectionViewFlowLayout</code>, and i want to calculate its content size (for return in <code>intrinsicContentSize</code> needed for adjusting its height via AutoLayout). </p>
  
  <p>The problems is: Even if I have a fixed and equal height for all cells, I don't know how many "rows"/lines I have in the <code>UICollectionView</code>. I also can't determine that count by the number of items in my data source, since the cells representing the data items vary in width, so does consequently the number of items I have in one line of the <code>UICollectionView</code>.</p>
  
  <p>Since I couldn't find any hints on this topic in the official documentation and googling didn't bring me any further, any help and ideas would be appreciated very much.</p>