How is touch event handling on the screen implemented in UIKit?

In UIKit, touch event handling occurs through an event system that passes touch events to UIResponder objects. The main methods for handling touches are methods from UIResponder:

• touchesBegan(_:with:) — called when a touch begins.
• touchesMoved(_:with:) — called when a finger moves on the screen.
• touchesEnded(_:with:) — called when a touch ends.
• touchesCancelled(_:with:) — called if the system cancels the touch (e.g., an incoming call).

These methods can be overridden in UIView or UIViewController to handle touches. Events are passed through the view hierarchy, starting from the topmost view where the touch occurred.

Example of overriding in UIView:

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    super.touchesBegan(touches, with: event)
    print("Touch began")
}