referenceSizeForHeaderInSection method error - ios

Question

I am trying to add a headerCell to a UICollectionView and am trying to call the referenceSizeForHeaderInSection method. I have created a collectionViewCell (ProfileCell) and it builds correctly, until I call the the referenceSizeForHeaderInSection method, then it crashes...not sure why. Thanks in advance for any and all help!
// UICollectionViewCell class *******
class ProfileCell: UICollectionViewCell {
override init(frame: CGRect) {
super.init(frame: frame)
setupViews()
}
let wordLabel: UILabel = {
let label = UILabel()
label.text = "test test test"
label.translatesAutoresizingMaskIntoConstraints = false
return label
}()
func setupViews() {
backgroundColor = .red
addSubview(wordLabel)
wordLabel.topAnchor.constraint(equalTo: self.topAnchor).isActive = true
wordLabel.leftAnchor.constraint(equalTo: self.leftAnchor).isActive = true
wordLabel.bottomAnchor.constraint(equalTo: self.bottomAnchor).isActive = true
wordLabel.rightAnchor.constraint(equalTo: self.rightAnchor).isActive = true
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
}
// UIViewController *******
class HomeController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate, UICollectionViewDelegateFlowLayout, FBSDKLoginButtonDelegate {
lazy var collectionView: UICollectionView = {
let layout = UICollectionViewFlowLayout()
layout.scrollDirection = .horizontal
layout.minimumLineSpacing = 0
let cv = UICollectionView(frame: .zero, collectionViewLayout: layout)
cv.delegate = self
cv.dataSource = self
cv.isPagingEnabled = true
return cv
}()
let cellId = "cellId"
let headerId = "headerId"
override func viewDidLoad() {
super.viewDidLoad()
view.addSubview(collectionView)
// use autolayout instead
collectionView.anchorToTop(view.topAnchor, left: view.leftAnchor, bottom: view.bottomAnchor, right: view.rightAnchor)
collectionView.backgroundColor = .white
collectionView.register(ProfileCell.self, forCellWithReuseIdentifier: cellId)
collectionView.register(UICollectionViewCell.self, forSupplementaryViewOfKind: UICollectionElementKindSectionHeader, withReuseIdentifier: headerId)
fileprivate func registerCells() {
collectionView.register(ProfileCell.self, forCellWithReuseIdentifier: cellId)
}
// set up collectionView
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 4
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: cellId, for: indexPath)
return cell
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return CGSize(width: view.frame.width, height: 150)
}
func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
let header = collectionView.dequeueReusableCell(withReuseIdentifier: headerId, for: indexPath)
return header
}
// crashes when I call this method
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForHeaderInSection section: Int) -> CGSize {
return CGSize(width: view.frame.width, height: 50)
}
}