UICollectionViewController与UITableViewController类似
在初始化中cell

self.collectionView!.register(ClassifyCell.self, forCellWithReuseIdentifier:reuseIdentifier)

基本的代理

override func numberOfSections(in collectionView: UICollectionView) -> Int {
        return 1
    }


    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 1
    }
    
    override func collectionView(_ collectionView: UICollectionView, shouldSelectItemAt indexPath: IndexPath) -> Bool {
        return true
    }

    override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath)
        return cell
    }

在初始化是要先创建

let layout = UICollectionViewFlowLayout.init()
        layout.itemSize = CGSize(width: width, height: height)
        let vc:UICollectionViewController = UICollectionViewController.init(collectionViewLayout: layout)

已防止报UICollectionView must be initialized with a non-nil layout parameter的错