         tickBox.borderStyle = .square
         tickBox.checkmarkStyle = .tick
         tickBox.checkmarkSize = 0.7
+        tickBox.valueChanged = { (value) in
+            print("tickBox value change: \(value)")
+        }
         view.addSubview(tickBox)
     }
 
     // target action example
     @objc func circleBoxValueChanged(sender: Checkbox) {
-        print("circle box value change: \(sender.isChecked)")
+        print("circleBox value change: \(sender.isChecked)")
     }
 
 }

        squareBox.uncheckedBorderColor = .lightGray
        squareBox.borderWidth = 1
        squareBox.valueChanged = { (value) in
            print("square checkbox value change: \(value)")
        }
        view.addSubview(squareBox)


        crossBox.borderStyle = .square
        crossBox.checkmarkStyle = .cross
        crossBox.checkmarkSize = 0.7
        crossBox.cornerRadius = 5
        crossBox.valueChanged = { (value) in
            print("crossBox value change: \(value)")
        }
        view.addSubview(crossBox)

        // tick
