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

Default Implementations

We have said several times now that interfaces focus on the what and not the how. You can, however, provide a default implementation for property getters and functions in an interface. Classes that implement the interface then have the option of using the default or defining their own implementation.

Provide a default implementation for attack in Fightable. This function should take the sum of the dice rolls and deal the corresponding amount of damage.

Listing 17.5  Defining a default implementation (Creature.kt)

import kotlin.random.Random

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

    fun takeDamage(damage: Int)

    fun attack(opponent: Fightable) {
        val ...