chiahsien/CHTCollectionViewWaterfallLayout — pull request #25 by olivercameron (2013-10-27 16:27:42+00:00)
Title: Add a 'respondsToSelector:' check for 'collectionView:heightForHeaderInLayout:'

Since *'collectionView:heightForHeaderInLayout:'* is an optional delegate method, a *'respondsToSelector:'* check should be added within *'layoutAttributesForElementsInRect:'*. Without the check you will receive an unrecognized selector crash.