Does Objective-C support traits/mixins?

Question

Are there any techniques for emulating traits or mixins in Objective-C?

In Scala, for example, I can do something like this:

trait ControllerWithData         


        

Answer 1

Traits or Mixins are not supported by Objective-C, you only have built-in option of Categories. But fortunately Objective-C Runtime has almost all tools for implementing own idea if mixing or traits with adding methods and properties to your class at runtime. You can read more about opportunities which Objective-C Runtime provides for you on Apple's documentation website Objective-C Runtime Docs

The idea is:

1) You can create an Objective-C protocol (Mixin), in which you will declare properties and methods.

2) Then you create a class (Mixin implementation), which will implement methods from this protocol.

3) You make your some class, in which you want to provide the possibility of composition with mixins, to conform that protocol (Mixin).

4) When your application launches, you add with Objective-C runtime all implementations from (Mixin implementation) class and properties declared in (Mixin) into your class.

5) voilà :)

Or you can use some ready open source projects such as "Alchemiq"