Functional Kotlin

Companion objects

Objects declared inside a class/interface can be marked as companion objects. Observe the use of companion objects in the following code:

class Cupcake(flavour: String) : BakeryGood(flavour), Bakeable {  override fun name(): String {     return "cupcake"   }     companion object {     fun almond(): Cupcake {       return Cupcake("almond")     }     fun cheese(): Cupcake {       return Cupcake("cheese")     }   } }

Now, methods inside the companion object can be used directly, using the class name without instantiating it:

fun main(args: Array<String>) {    val myBlueberryCupcake: BakeryGood = Cupcake("Blueberry")    val myAlmondCupcake = Cupcake.almond()    val myCheeseCupcake = Cupcake.cheese()    val myCaramelCupcake = Cupcake("Caramel")}

Companion object's methods ...