sample.kt

package com.banshee.kotlinsamplecode

class KotlinSample {
    data class Holder(val x: Int, val s: String)

    companion object {
        // one of these for all instances of KotlinSample
    }

    val x = com.banshee.kotlinsamplecode.KotlinSampleObject.fn("whatever")

    fun fn() {
        // Destructuring https://kotlinlang.org/docs/reference/multi-declarations.html
        val (h1, h2) = Holder(1, "stuff")

        // when is better than most languages switch statements,
        // but it's not pattern matching like Scala
        when {
            x == 1 -> "one"
            else -> "default"
        }
        when (x) {
            1 -> "one"
            else -> "default"
        }
        // you can introduce a binding in the when argument
        val result: Int = when (val t = x) {
            1 -> t
            else -> t + 1
        }
    }
}

// object creates a singleton (per classloader though; that's not relevant for Android)
object KotlinSampleObject {
    // Type parameters are specified with <T>
    fun <T> fn(t: T): Int {
        return 3
    }

    inline fun <reified T> inlineFn(x: T): T {
        return x
    }
}

object ScopeFunctions {
    // https://kotlinlang.org/docs/reference/scope-functions.html
    fun samples() {
        // let, run, with, apply, and also.
        val letResult: Int = "something".let {
            // it is "something"
            // returns the result of the block
            3
        }
        val runResult: Int = "something".run {
            // this is "something"
            // returns the result of the block
            3
        }
        val withResult: Int = with("something") {
            // this is "something"
            // returns the result of the block
            length
        }

        // apply and also are for fluent calls - they return the context object
        val applyResult: String = "something".apply {
            // this is "something"
            // returns "something"
        }
        val alsoResult: String = "something".also {
            // it is "something"
            // returns "something"
        }

        // you can also use run to run a block
        val runResultByItself = run {
            1
            2
            3
        }
    }
}