Hands-On Design Patterns with Kotlin

State of the Nation

The previous approach has most of the logic in our context. You may sometimes see a different approach, which is valid as your context grows bigger.

In this approach, Snail would become really thin:

class Snail {    internal var mood: Mood = Still(this)    private var healthPoints = 10    // That's all!}

Note that we marked mood as internal. That lets other classes in that package alter it.

Instead of Snail implementing WhatCanHappen, our Mood will:

sealed class Mood : WhatCanHappen

And now the logic resides within our state objects:

class Still(private val snail: Snail) : Mood() {    override fun seeHero() = snail.mood.run {            Aggressive(snail)        }    override fun getHit(pointsOfDamage: Int) = this    override fun timePassed() = this}

Note ...