UIViewController section headers not showing - ios

Question

I have a UICollectionView with several headers.
They are implemented as section headers.
Each header belongs to its own controller and those controllers conform to MyHeaderProtocol.
Basically I have an array of controllers and request header cell from each of them when necessary.
So:
collectionView(:viewForSupplementaryElementOfKind:at) is called and returns actual view. View is properly set, has good frame size etc. Just in case I color view there to purple - but I can't see it on screen.
collectionView(_:layout:referenceSizeForHeaderInSection:) is called and return good CGSize values.
Collection view is displayed but instead of all those headers I see just empty white space.
So the issue is - both necessary methods do display a header section are called but section header isn't displayed (yet space is reserved for it).
Here is simplified version of my code:
protocol MyHeaderProtocol: class {
var nib: UINib { get }
var cellReuseIdentifier: String { get }
// Will dequeue UICollectionViewCell using dequeueReusableSupplementaryView and set data for this cell
func setupHeader(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: IndexPath) -> UICollectionViewCell?
func getCellHeight()
}
class MyCollectionView: UIViewController {
#IBOutlet private weak var collectionView: UICollectionView
private var headers: [MyHeaderProtocol] = []
override func viewDidLoad() {
super.viewDidLoad()
collectionView.delegate = self
collectionView.dataSource = self
// it will instantiate controllers conformed to MyHeaderProtocol and append them to header array
setUpHeaders()
registerHeaders()
}
private func setUpHeaders() {
let headerOne = SimpleHeader1(withModel: viewModel)
headers.append(headerOne)
let headerTwo = SimpleHeader2(withModel: viewModel)
headers.append(headerTwo)
}
private func registerHeaders() {
for header in headers {
collectionView.register(header.nib, forSupplementaryViewOfKind: UICollectionElementKindSectionHeader, withReuseIdentifier: header.cellReuseIdentifier)
}
}
}
extension MyCollectionView: UICollectionViewDataSource {
func numberOfSections(in collectionView: UICollectionView) -> Int {
return headers.count + 1
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
if section == headers.count {
// If section isn't a header section - we return actual cells
return viewModel.people.count
} else {
// if it is a header - we return only section, no intems
return 0
}
}
func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
var view : UICollectionReusableView?
switch kind {
case UICollectionElementKindSectionHeader:
// if it is a header
if indexPath.section < headers.count {
let header = headers[indexPath.section]
view = header.setupHeader(collectionView: collectionView, cellForItemAtIndexPath: indexPath)
// to test that header is visible
view?.backgroundColor = UIColor.purple
}
case UICollectionElementKindSectionFooter:
break
default:
assert(false, "Unexpected element kind")
break
}
return view ?? UICollectionReusableView()
}
}
extension MyCollectionView : UICollectionViewDelegateFlowLayout{
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForHeaderInSection section: Int) -> CGSize {
var size = CGSize.zero
// If that's header - return non-Zero size
if section < headers.count {
let header = headers[section]
size = CGSize.init(width: collectionView.bounds.width, height: header.getCellHeight())
}
return size
}
}

Answer 1

I think the issue may be with your custom MyHeaderProtocol protocol. This function in particular:
func setupHeader(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: IndexPath) -> UICollectionViewCell?
You have to return a header here, otherwise this function collectionView(:viewForSupplementaryElementOfKind:at will not produce expected behaviour:
var view : UICollectionReusableView?
view = header.setupHeader(collectionView: collectionView, cellForItemAtIndexPath: indexPath)
So try this instead:
func setupHeader(collectionView: UICollectionView, headerForItemAtIndexPath indexPath: IndexPath) -> UICollectionReusableView
I hope this helps.