kotlin cheatsheet

2022-09-17
  • cheatsheet
  • kotlin

    • Scope function

    Function Object reference Return value Is extension function
    let it Lambda result Yes
    run this Lambda result Yes
    run - Lambda result No: called without the context object
    with this Lambda result No: takes the context object as an argument
    apply this Object reference Yes
    also it Object reference Yes 
            var expect = ""
        expect =
            with("hello") { // inline fun <T, R> with(receiver: T, block: T.() -> R): R {
                logger.info("$this, world")
                return@with substring(0, 3) + "with"
            }
        Assertions.assertEquals("helwith", expect)

        expect =
            "hello".also { // inline fun <T> T.also(block: (T) -> Unit): T
                logger.info("$it, world")
            }
        Assertions.assertEquals("hello", expect)

        expect =
            "hello".apply { // inline fun <T> T.apply(block: T.() -> Unit): T
                logger.info("$this, world")
            }
        Assertions.assertEquals("hello", expect)

        expect =
            "hello".let { // inline fun <T, R> T.let(block: (T) -> R): R
                logger.info("$it, world")
                return@let it.substring(0, 3) + "let"
            }
        Assertions.assertEquals("hellet", expect)

        expect =
            "hello".run { // inline fun <T, R> T.run(block: T.() -> R): R
                logger.info("$this, world")
                return@run substring(0, 3) + "run"
            }
        Assertions.assertEquals("helrun", expect)

        expect = run { // inline fun <T, R> T.run(block: T.() -> R): R
            val hello = "hello"
            logger.info("$hello, world")
            hello
        }
        Assertions.assertEquals("hello", expect)

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