Editing Delegation pattern (section)

== Language support ==
Some languages have special support for delegation built in. For example, in the [[Kotlin (programming language)|Kotlin]] programming language the <code>by</code> keyword<ref>{{Cite web|url=https://kotlinlang.org/docs/reference/delegation.html|title=Delegation - Kotlin Programming Language|website=Kotlin|access-date=2019-03-23}}</ref> delegates to another object's interface:

<syntaxhighlight lang="kotlin">interface ClosedShape {
    fun area(): Int
}

class Rectangle(val width: Int, val height: Int) : ClosedShape {
    override fun area() = width * height
}

// The ClosedShape implementation of Window delegates to that of the Rectangle that is bounds
class Window(private val bounds: Rectangle) : ClosedShape by bounds</syntaxhighlight>