How does event handling on press occur in an application?

In iOS, touch event handling usually occurs through the Target-Action mechanism or Gesture Recognizers.

When a user taps on an element (for example, a UIButton), the system:

1. Tracks the touch event on the screen.
2. Determines which UI element was tapped.
3. Calls the method (action) associated with that element, registered for the event, such as touchUpInside.

Example with UIButton:

let button = UIButton(type: .system)
button.addTarget(self, action: #selector(buttonTapped), for: .touchUpInside)

@objc func buttonTapped() {
    print("Button tapped")
}

You can also use UIGestureRecognizer for more complex gestures, such as tap, swipe, etc. They are added to a UIView and invoke methods upon recognizing the gesture.

Thus, touch event handling is the application's response to system touch events, associated with calling the appropriate methods in the code.