Kotlin let, also, run, apply

kotlin_let_also_run_apply.kt

package org.vld.kotlin.language

class Demo(private val property: String = "Demo") {

    fun runExample() {
        // run > transformation function > this > returns new value
        val string = "run Kotlin".run {
            println(this)
            "run Kotlin 1.2.20"
        }
        println(string)
    }

    fun letExample() {
        // let > transformation function > it + outer this > returns new value
        val string = "let Kotlin".let {
            println("let ${this.property}")
            println(it)
            "let Kotlin 1.2.20"
        }
        println(string)
    }

    fun applyExample() {
        // apply > mutating operation > this > returns original object
        val string = "apply Kotlin".apply {
            println(this)
        }
        println(string)
    }

    fun alsoExample() {
        // also > mutating operation > it + outer this > returns original object
        val string = "also Kotlin".also {
            println("also ${this.property}")
            println(it)
        }
        println(string)
    }
}

fun main(args: Array<String>) {
    val demo = Demo()
    with(demo) {
        runExample()
        // run Kotlin
        // run Kotlin 1.2.20
        letExample()
        // let Demo
        // let Kotlin
        // let Kotlin 1.2.20
        applyExample()
        // apply Kotlin
        // apply Kotlin
        alsoExample()
        // also Demo
        // also Kotlin
        // also Kotlin
    }
}