Call other class function before its own class in iOS

Question

I created a checkbox button with class CheckBox . I want to enable/disable ResultTextField according to the value of checkbox ischecked . So i linked a button with @IBAction func retestRequestedCheckbox_onChange() . The proble is the func retestRequestedCheckbox_onChange() is getting called before it updated value in CheckBox class. How can i update the checkbox value before calling retestRequestedCheckbox_onChange() function? Here is my code:

class Checkbox: UIButton {

    let checkedImage = UIImage(named: "checked_checkBox") as UIImage?
    let unCheckedImage = UIImage(named: "unchecked_checkBox") as UIImage?
    var isChecked:Bool = false{
        didSet
        {
            if isChecked == true{
                self.setImage(checkedImage, forState: .Normal)
            }else {
                self.setImage(unCheckedImage, forState: .Normal)
            }
        }
    }

    override func awakeFromNib() {
        self.addTarget(self, action: "buttonClicked:", forControlEvents: UIControlEvents.TouchUpInside)
    self.isChecked = false
    }

    func buttonClicked(sender: UIButton){
        if(sender == self){
            if isChecked == true {
                isChecked = false
            } else {
                isChecked = true
            }
        }
    }

}

 @IBAction func Checkbox_onChange(){


        if CheckboxButton.isChecked ?? false {
           ResultTextField.enabled = true

        } else {
          ResultTextField = false    
        }

}

Answer 1

为什么不简单地将用于更改UI的代码放在didSet方法中？