What is the “right” way to handle orientation changes in iOS 8?

Question

Can someone please tell me the \"right\" or \"best\" approach to working with portrait and landscape interface orientations in iOS 8? It seems that all the functions I want

Answer 1

Based on smileyborg's very well detailed (and accepted) answer, here is an adaptation using swift 3:

override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
    super.viewWillTransition(to: size, with: coordinator)
    coordinator.animate(alongsideTransition: nil, completion: {
        _ in
        self.collectionView.collectionViewLayout.invalidateLayout()
    })        
}

And in the UICollectionViewDelegateFlowLayout implementation,

public func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
    // retrieve the updated bounds
    let itemWidth = collectionView.bounds.width
    let itemHeight = collectionView.bounds.height
    // do whatever you need to do to adapt to the new size
}