Kotlin Programming: The Big Nerd Ranch Guide, 2nd Edition

Defining an Interface

To define how combat is performed, you will first create an interface that specifies the functions and properties used for entities in the game when performing combat. Your player will face goblins, but you will define a combat system that can be applied to any type of creature – not just goblins.

Create a new file called Creature.kt – in the com.bignerdranch.nyethack package, to avoid naming collisions – and define a Fightable interface, using the keyword interface:

Listing 17.1  Defining an interface (Creature.kt)

interface Fightable {
    val name: String
    var healthPoints: Int
    val diceCount: Int
    val diceSides: Int

    fun takeDamage(damage: Int)

    fun attack(opponent: Fightable)
}

Your interface declaration ...