Is there any way to DRY my Objective-C iOS ViewControllers?

Question

I have a group of controllers, most of whom share similar functionality.

For example:

• Controller A has method 1 and method 2.
• Controller B has method 2 and method 3.
• Controller C has method 1 and method 3.

Subclassing is not really an option here as I specifically don't want Controller B to have method 1.

Protocols are not really ideal either; They still require me to define duplicates of my methods in each controller.

Is there no way to define a method in one place and mix this functionality into classes as and when required in Objective C?

Answer 1

Use blocks! https://developer.apple.com/library/ios/#documentation/Cocoa/Conceptual/Blocks/Articles/00_Introduction.html#//apple_ref/doc/uid/TP40007502

Answer 2

A possibility is not to use a class at all. Since I guess those methods require to access some of your controllers' fields, you can use a function that receive as a parameter a pointer to a UIViewController and access its fields from inside the function.
If each method should behave in a slightly different way depending if you are working with a ControllerA,ControllerB or ControllerC, then you can use isKindOfClass method. For example:

    void method1(UIViewController* controller) {
        if( [(id) controller isKindOfClass:[ControllerA class]] ) {
             //do something
        }
    }