Recently we had the need of presenting our entries in a kind of gallery in one of our apps. This is not supposed to be a big problem, as in iOS6 the new UICollectionView was introduced, however we were not allowed yet to drop the support for iOS5 so we were basically screwed.
By looking at a solution to this problem i found the PSTCollectionView that was developed by Peter Steinberger for one of his projects, but fortunately he put it open source onto GitHub.
From the functionalities and the look&feel its almost a 1:1 copy of the native UICollectionView but it works all the way down to iOS 4.3, which is great, as we just need it to work on iOS5. The best feature in my opinion is the full interoperability with the native UICollectionView classes and helper classes.
This means, that you're able to use native classes if they are present (so if its running on >iOS6.0) otherwise there is a build in fallback to the custom PSTCollectionView classes. All you need to do in your code (beside providing the library files) is to change the definitions from e.g. UICollectionView to PSUICollectionView, UICollectionViewDelegate to PSUICollectionViewDelegate, and so on. The rest is performed in the background.
Installing it into your project is simple as well, mainly if you use CocoaPods, which I'll discuss in a future article.