为什么UIButton可以向私有方法发送消息？

Question

In the first case in the book iOS programming: The Big Nerd Ranch Guide, they only implemented a method - (IBAction)showQuestion:(id)sender between the @implementation @end , but did not declare it in the @interface @end in the .h file. As far as I know, if you don't declare methods in the @interface @end , the method cannot be accessed from outside. But the truth is the UIButton did send message to the controller instance, that confused me. Do I have a wrong idea about private method?

Answer 1

InterfaceBuilder looks in all source files, headers and implementation, to find IBOutlets and IBActions. Private or not, it sees all declared methods, so you can connect them to interface components. During runtime, all methods are equal, so of course the button can call a private method.