Swift 3-自定义UIButton radius删除约束？

let button = UIButton()
button.translatesAutoresizingMaskIntoConstraints = false
self.view.addSubview(button)

// 添加约束
button.centerXAnchor.constraint(equalTo: self.view.centerXAnchor).isActive = true
button.centerYAnchor.constraint(equalTo: self.view.centerYAnchor).isActive = true
button.widthAnchor.constraint(equalToConstant: 200).isActive = true
button.heightAnchor.constraint(equalToConstant: 50).isActive = true

button.layer.cornerRadius = button.frame.height / 2
button.layer.masksToBounds = true

button.removeConstraints(button.constraints)