NSLayoutAnchorの使い方

Question

NSLayoutAnchorのequalToにこの場合なにを入れればいいのですか？
いろいろ試したものの毎回Use of unresolved identifierと出ます。

class HomeController: UICollectionViewController, UICollectionViewDelegateFlowLayout  {
    

    override func viewDidLoad() {
        super.viewDidLoad()
        navigationItem.title = "Home"
        
        collectionView?.backgroundColor = UIColor.white

        collectionView?.register(VideoCell.self, forCellWithReuseIdentifier: "cellid")
        
    }
    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 5
    }
    override 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: 200.0)
    }
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
        return 0
    }
 
}

class VideoCell: UICollectionViewCell {
    override init(frame: CGRect) {
        super.init(frame: frame)
        setupView()
    }
    
    let thumbnailImageView: UIImageView = {
        let imageView = UIImageView()
        imageView.backgroundColor = UIColor.blue
        imageView.translatesAutoresizingMaskIntoConstraints = false
        return imageView
    }()
    
//    let separatorView: UIView = {
//        let view = UIView()
//        view.backgroundColor = UIColor.black
//        view.translatesAutoresizingMaskIntoConstraints = false
//        return view
//    }()
    

     func setupView(){
        addSubview(thumbnailImageView)
//        addSubview(separatorView)
        
        thumbnailImageView.centerXAnchor.constraint(equalTo: .centerXAnchor)
        
        
    }
        required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

Answer 1

NSLayoutConstraint.activate([
    thumbnailImageView.centerXAnchor.constraint(equalTo: contentView.centerXAnchor),
    thumbnailImageView.centerYAnchor.constraint(equalTo: contentView.centerYAnchor)
    thumbnailImageView.widthAnchor.constraint(equalToConstant: 30),
    thumbnailImageView.heightAnchor.constraint(equalToConstant: 30),
])

みたいにします。

ちゃんとできてますが、addSubviewよりあとでよぶことと、 .translatesAutoresizingMaskIntoConstraints = false にすることに注意して下さい。