How can responsibility be delineated between controller components and the user interface?

Responsibility separation between the controller and the user interface in iOS is usually achieved through architectural patterns such as MVC or MVVM.

• The controller (UIViewController) is responsible for handling user actions, managing the screen's lifecycle, and interacting with the data model.
• The user interface (UIView and its subclasses) is only responsible for displaying data and visual presentation.

Thus, the controller should not contain display logic, and the interface should not contain business logic. This improves code readability and maintainability.