UICollectionReusableView method not being called

Question

I want my sections in the UICollectionView to have a header with an image.

I have followed these steps:

• at the storyboard, assigned a header a

Answer 1

Swift 3.0 (xcode 8.2.1)

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForHeaderInSection section: Int) -> CGSize {
    return CGSize(width:collectionView.frame.size.width, height:30.0)
}