Hands-On Object-Oriented Programming with Kotlin

Decorator

The decorator pattern allows us to add behavior to the individual object dynamically, without affecting the behavior of other objects from the same class. We can achieve this by wrapping the object into another instance. The following diagram shows a case like this:

The diagram contains the AmateurCoffeeMachine and ProfessionalCoffeeMachine classes, which implement the CoffeeMachine interface.

The following example shows how this pattern works:

interface CoffeeMachine {    val leftCoffeeMilliliters: Int     val leftMilkMilliliters: Int         fun makeCoffee(milliliters: Int): Coffee {        leftCoffeeMilliliters - milliliters        return Coffee(milliliters) ...