如果它们的总宽度大于UICollectionView UICollectionViewCell，则裁剪最后一个宽度

import UIKit

class ViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
    
    var collectionView: UICollectionView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let layout = UICollectionViewFlowLayout()
        layout.scrollDirection = .horizontal
        collectionView = UICollectionView(frame: .zero, collectionViewLayout: layout)
        collectionView.dataSource = self
        collectionView.delegate = self
        collectionView.register(CustomCell.self, forCellWithReuseIdentifier: "cell")
        view.addSubview(collectionView)
        
        // 设置约束
        collectionView.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            collectionView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            collectionView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            collectionView.topAnchor.constraint(equalTo: view.topAnchor),
            collectionView.bottomAnchor.constraint(equalTo: view.bottomAnchor)
        ])
    }
    
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 10
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath) as! CustomCell
        cell.configure(with: "Item \(indexPath.item)")
        return cell
    }
    
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        return CGSize(width: collectionView.bounds.width / 3, height: 100)
    }
}

class CustomCell: UICollectionViewCell {
    let label = UILabel()
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        contentView.addSubview(label)
        label.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            label.leadingAnchor.constraint(equalTo: contentView.leadingAnchor),
            label.trailingAnchor.constraint(equalTo: contentView.trailingAnchor),
            label.topAnchor.constraint(equalTo: contentView.topAnchor),
            label.bottomAnchor.constraint(equalTo: contentView.bottomAnchor)
        ])
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    func configure(with text: String) {
        label.text = text
    }
}