Should I implement functions inside the class to adapt MVC?

I'm new to design patterns. I have a class called CustomClass which is a subclass of UILabel, I'm using Swift, within the app I'd perform several operations to instances of this class, such as rotating, resizing and etc..

Now it's the question, I can either implement these functions within the class or their parent ViewController, which is the right way in order to adapt the app to the MVC?