CODESAMPLE

Template Method - Kotlin

Template Method Kotlin

The Template Method pattern defines the skeleton of an algorithm in a base class, deferring some steps to subclasses. It allows subclasses to redefine certain steps of an algorithm without changing the algorithm’s structure. This promotes code reuse and avoids duplication.

The Kotlin example defines an abstract Game class with a play() method representing the algorithm’s skeleton. initialize(), start(), run() and end() are abstract methods that subclasses must implement, providing the specific steps. Concrete game classes like Cricket and Football inherit from Game and provide their own implementations for these steps, while the overall play() sequence remains consistent. Kotlin’s abstract classes and methods naturally support this pattern, and the use of concise function definitions aligns with Kotlin’s style.

abstract class Game {
    abstract fun initialize()
    abstract fun start()
    abstract fun run()
    abstract fun end()

    fun play() {
        println("Game: Starting...")
        initialize()
        start()
        run()
        end()
        println("Game: Finished.")
    }
}

class Cricket : Game() {
    override fun initialize() {
        println("Cricket: Initializing the game...")
    }

    override fun start() {
        println("Cricket: Starting the match...")
    }

    override fun run() {
        println("Cricket: Playing the innings...")
    }

    override fun end() {
        println("Cricket: Match ended.")
    }
}

class Football : Game() {
    override fun initialize() {
        println("Football: Preparing the field...")
    }

    override fun start() {
        println("Football: Kickoff!")
    }

    override fun run() {
        println("Football: Playing two halves...")
    }

    override fun end() {
        println("Football: Game over.")
    }
}

fun main() {
    val cricketGame = Cricket()
    cricketGame.play()

    println("\n--- Next Game ---\n")

    val footballGame = Football()
    footballGame.play()
}