How is event handling implemented in the UIKit framework?

In UIKit, event handling is based on the responder chain and the event loop system.

When a user interacts with the application (for example, taps on the screen), the system creates an event (such as a touch) and passes it to the application. The event passes through a chain of UIResponder objects — starting from the lowest level (for example, the UIView where the touch occurred) and moving up the hierarchy (UIViewController, UIWindow, UIApplication).

Each object in the chain can handle the event or pass it further. If the event is not handled, it is ignored.

To manage events in UIKit, the following methods are used:

• touchesBegan(:with:), touchesMoved(:with:), touchesEnded(_:with:) for touches;
• UIControl sends actions via the target-action mechanism;
• UIGestureRecognizer recognizes gestures and responds to them.

Thus, event handling in UIKit is a combination of the responder chain, target-action, and gesture recognizers, providing flexible hierarchical processing of user interactions.