纯代码生成集合，但不执行UICollectionViewDelegateFlowLayout

let collectionView = UICollectionView(frame: CGRect(x: 0, y: 0, width: 200, height: 200), collectionViewLayout: UICollectionViewFlowLayout())

collectionView.dataSource = self
collectionView.delegate = self

func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return data.count
}

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! CustomCell
    cell.textLabel.text = data[indexPath.item]
    return cell
}

class CustomCell: UICollectionViewCell {
    var textLabel: UILabel!
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        
        textLabel = UILabel(frame: bounds)
        textLabel.textAlignment = .center
        addSubview(textLabel)
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

view.addSubview(collectionView)