Functions returning function type.md

Functions returning function type

You can call a Kotlin function returning a lambda. The result has Swift function type, like () -> String, so you can easily call it.

Explanations

Let's describe a function that returns some kind of lambda in Kotlin:

// FunctionReturnsLambda.kt

fun returnLambda(): () -> Unit {
    println("Function that returns lambda")

    return {
        println("Lambda inside return")
    }
}

fun returnParametrizedLambda(): (String) -> Unit {
    println("Function that returns parametrized lambda")

    return {
        println("returnParametrizedLambda | it: $it")
    }
}

class FunctionReturnsLambdaExample() {
    fun example() {
        returnLambda()()
        returnParametrizedLambda()("123")
        println("FunctionReturnsLambdaExample: All ok")
    }
}

On the Swift side, this works correctly:

FunctionReturnsLambdaKt.returnLambda()()
FunctionReturnsLambdaKt.returnParametrizedLambda()("123")

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