什么条件逻辑可以用于swift中的子类布尔值?

我正在对uitextfield进行子类化,以便在右侧创建一个覆盖按钮,该按钮将切换IsSecureTextentry布尔值。通常,在故事板中创建IBactions时,布尔值是基于发送者确定的,我将在这样的目标C代码中实现发送者:

-(IBAction)showPasswordTapped:(UIButton *)sender{
   sender.selected = !sender.selected;
   self.passwordField.secureTextEntry = !sender.selected;
}

然而,既然我已经对其进行了子类化,我考虑使用if-else语句,但是逻辑看起来好像只会将布尔值设置回true。如果我没有访问发送者的权限,那么合适的条件语句是什么?

以下是我在Swift中的子类:

class SecurePasswordUITextField : UITextField {
    override func awakeFromNib() {
        super.awakeFromNib()
        self.isSecureTextEntry = true
        var overlayButton = UIButton.init(type: UIButtonType.custom)
        overlayButton.titleLabel = "Show"
        overlayButton.addTarget(self, action: #selector(showSecureCharacters), for: .touchUpInside)
        overlayButton = CGRect.init(x: self.bounds.origin.x, y: self.bounds.origin.y, width: 28, height: 28)
        self.rightView = overlayButton
        self.rightViewMode = UITextFieldViewMode.always
    }
    func showSecureCharacters(){
        if self.isSecureTextEntry {
            self.isSecureTextEntry = false
        } else {
            self.isSecureTextEntry = true
        }
        if !self.isSecureTextEntry{
            self.isSecureTextEntry = true
        } else {
            self.isSecureTextEntry = false
        }

    }
}