How is the mechanism of responding to user clicks implemented in the system?

In iOS, the response mechanism to a press is implemented through the event system and handlers (target-action). Usually, for buttons and other interactive elements, a target object and a method are assigned, which is called when the event occurs, such as a press.

Example in Swift:

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

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

Here, addTarget(_:action:for:) links the .touchUpInside event with the buttonTapped method. When pressed, the system calls this method, and you can perform the necessary actions.