将标签添加到UITextField

// 创建UILabel对象
let label = UILabel()
label.text = "Username:"
label.font = UIFont.systemFont(ofSize: 14)
label.textColor = UIColor.black

// 创建UITextField对象
let textField = UITextField()
textField.borderStyle = .roundedRect
textField.placeholder = "Enter username"

// 创建UIView对象
let containerView = UIView()

// 将UILabel和UITextField添加到UIView中
containerView.addSubview(label)
containerView.addSubview(textField)

// 使用Auto Layout布局
label.translatesAutoresizingMaskIntoConstraints = false
textField.translatesAutoresizingMaskIntoConstraints = false

NSLayoutConstraint.activate([
    label.leadingAnchor.constraint(equalTo: containerView.leadingAnchor),
    label.centerYAnchor.constraint(equalTo: containerView.centerYAnchor),
    textField.leadingAnchor.constraint(equalTo: label.trailingAnchor, constant: 8),
    textField.centerYAnchor.constraint(equalTo: containerView.centerYAnchor),
    textField.trailingAnchor.constraint(equalTo: containerView.trailingAnchor)
])

// 将UIView添加到主视图中
view.addSubview(containerView)