为什么我看不到这个标签上的约束?

class A19: UIView {
let titleLabel : UILabel = {
    let label = UILabel()
    label.text = "test"
    label.textColor = .white
    label.translatesAutoresizingMaskIntoConstraints = false
    return label
}()

init() {
    super.init(frame: CGRect(x: 0, y: 0, width: 414, height: 250))
    backgroundColor = .black
    addSubview(titleLabel)
    titleLabel.topAnchor.constraint(equalTo: topAnchor, constant: 20).isActive = true
    titleLabel.sizeToFit()
}

required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
}
}

这有什么不对?

编辑:所以我把操场,让每个人都看到我没有疯!