Why aren't my collection view cells showing...? - ios

Question

It's been a while since I programmatically created a collection view and I can't seem to find why my cells are not showing. Delegate and Datasource are being set. Size is being set and it is not too big.
class ViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
let cellId = "cellId"
override func viewDidLoad() {
super.viewDidLoad()
setupCV()
}
var containerCollectionView: UICollectionView = {
let layout = UICollectionViewLayout()
let cv = UICollectionView(frame: .zero, collectionViewLayout: layout)
cv.backgroundColor = UIColor.white
return cv
}()
}
extension ViewController {
fileprivate func setupCV() {
// these first two lines add the colelction view and apply constraints - they work and the CV is properly displayed inside the view controller
self.view.addSubview(containerCollectionView)
containerCollectionView.anchor(view.topAnchor, left: view.leftAnchor, bottom: view.bottomAnchor, right: view.rightAnchor, topConstant: 0, leftConstant: 0, bottomConstant: 0, rightConstant: 0, widthConstant: 0, heightConstant: 0)
containerCollectionView.delegate = self
containerCollectionView.dataSource = self
containerCollectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: cellId)
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return CGSize(width: 150, height: 150)
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: cellId, for: indexPath)
cell.backgroundColor = UIColor.yellow
return cell
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 3
}
}

Answer 1

You are initializing the wrong layout.
try this:
let layout = UICollectionViewFlowLayout()