How do applications respond to button presses?

The touch event sent by the operating system is processed.

Process:

1. The user touches the screen.
2. iOS registers the UITouch event.
3. The event is sent to the main window (UIWindow).
4. The window forwards the event to the responder chain (Responder Chain).
5. The button (UIButton) recognizes the press as a UIControlEventTouchUpInside event.
6. The UIButton calls the associated event handler method (target/action).

Example:

// Bind target/action for the "touch inside" event
button.addTarget(self, action: #selector(buttonTapped), for: .touchUpInside)

// Define the handler method
@objc func buttonTapped() {
    // Logic to execute after button press
    print("Button pressed!")
}

Responder Chain:

• UIView (button)
• The superview of the button
• The view controller (UIViewController)
• The window (UIWindow)
• The application delegate (UIApplicationDelegate)

The event moves up the chain until it is handled or rejected. UIButton usually handles touchUpInside itself.