通过UITextFields约束问题进行交换

// 创建两个UITextFields
let textField1 = UITextField()
let textField2 = UITextField()

// 设置约束
textField1.translatesAutoresizingMaskIntoConstraints = false
textField2.translatesAutoresizingMaskIntoConstraints = false

NSLayoutConstraint.activate([
    textField1.topAnchor.constraint(equalTo: view.topAnchor, constant: 100),
    textField1.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 20),
    
    textField2.topAnchor.constraint(equalTo: textField1.bottomAnchor, constant: 20),
    textField2.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 20),
])

// 创建交换按钮
let swapButton = UIButton()
swapButton.setTitle("Swap", for: .normal)
swapButton.addTarget(self, action: #selector(swapTextFields), for: .touchUpInside)

// 实现交换逻辑
@objc func swapTextFields() {
    let tempText = textField1.text
    textField1.text = textField2.text
    textField2.text = tempText
}

// 添加到视图
view.addSubview(textField1)
view.addSubview(textField2)
view.addSubview(swapButton)