这里我有一个问题，我有一个stackView它包含5个元素，它们被赋予了topAnchor，LEADED，bottom，traling和padding，它们有相同的宽度大小，我想改变SelectPhoto:UIButton的宽度，但是因为它在stackView中它没有改变，我如何改变或者调用一个数组（stackView）中的一个元素，并且改变？ 事情应该是这样的:

创建元素:

    let selectImageButton : UIButton = {
    let button = UIButton(type: .system)
    button.setTitle("Select Photo", for: .normal)
    button.titleLabel?.font = UIFont.systemFont(ofSize: 28, weight: .light)

    button.backgroundColor = .white
    button.setTitleColor(#colorLiteral(red: 0.4149784446, green: 0.4487785101, blue: 0.8248928785, alpha: 1), for: .normal)
    return button
}()

let userNameTextField : CustomTextField = {
    let textField = CustomTextField(padding: 16)
    textField.placeholder = "Username"
    textField.backgroundColor = .white
    return textField
}()

let emailTextField : CustomTextField = {
    let textField = CustomTextField(padding: 16)
    textField.placeholder = "Email"
    textField.keyboardType = .emailAddress
    textField.backgroundColor = .white
    return textField
}()

正在添加StackView:

 lazy var stackView = UIStackView(arrangedSubviews: [
              selectImageButton,
              userNameTextField,
              emailTextField,
              passwordTextField,
              registrationButton
              ])

约束条件:

fileprivate func addingSettingStackView(_ stackView: UIStackView) {
      view.addSubview(stackView)
      stackView.axis = .vertical
      stackView.spacing = 8
      stackView.anchor(top: nil, leading: view.leadingAnchor, bottom: nil, trailing: view.trailingAnchor,padding: .init(top: 0, left: 50, bottom: 0, right: 50))
    stackView.centerYAnchor.constraint(equalTo: view.centerYAnchor, constant: 100).isActive = true
  }