Functional Kotlin

Extension functions for objects

In Kotlin, objects are a type, therefore they can have functions, including extension functions (among other things, such as extending interfaces and others).

We can add a buildBridge extension function to the object, Builder:

object Builder {}fun Builder.buildBridge() = "A shinny new bridge"

We can include companion objects. The class Designer has two inner objects, the companion object and Desk object:

class Designer {   companion object {   }   object Desk {   }}fun Designer.Companion.fastPrototype() = "Prototype"fun Designer.Desk.portofolio() = listOf("Project1", "Project2")

Calling this functions works like any normal object member function:

Designer.fastPrototype()Designer.Desk.portofolio().forEach(::println) ...