How to use addTarget method in swift 3

Yes, don't add "()" if there is no param

button.addTarget(self, action:#selector(handleRegister), for: .touchUpInside). 

and if you want to get the sender

button.addTarget(self, action:#selector(handleRegister(_:)), for: .touchUpInside). func handleRegister(sender: UIButton){   //...}

Edit:

button.addTarget(self, action:#selector(handleRegister(_:)), for: .touchUpInside)

no longer works, you need to replace _ in the selector with a variable name you used in the function header, in this case it would be sender, so the working code becomes:

button.addTarget(self, action:#selector(handleRegister(sender:)), for: .touchUpInside)

Try this with Swift 4

buttonSection.addTarget(self, action: #selector(actionWithParam(_:)), for: .touchUpInside)@objc func actionWithParam(sender: UIButton){    //...}buttonSection.addTarget(self, action: #selector(actionWithoutParam), for: .touchUpInside)@objc func actionWithoutParam(){    //...}

Try this

button.addTarget(self, action:#selector(handleRegister()), for: .touchUpInside). 

Just add parenthesis with name of method.

Also you can refer link : Value of type 'CustomButton' has no member 'touchDown'