What is the role of the Delegation pattern in object-oriented programming and why is it used?

The Delegation pattern in object-oriented programming is a way of passing responsibility for executing a specific task to another object. Instead of the class implementing some functionality itself, it delegates it to another object that specializes in that task.

This allows:

• To divide responsibilities among classes, improving modularity.
• To increase code reuse.
• To simplify support and extension of functionality.
• To avoid inheritance where composition is sufficient.

For example, in Android, delegation is often used for event handling: an activity delegates button click handling to a separate listener object.

class ButtonHandler {
    fun onClick() {
        println("Button clicked")
    }
}

class Activity {
    private val handler = ButtonHandler()

    fun buttonClicked() {
        handler.onClick()  // delegating handling
    }
}