Functions with default arguments.md

Functions with default arguments

You always have to specify all the function arguments. Improved interop available with SKIE.

Explanations

In Kotlin, you can omit specifying the values of function arguments if they have default values:

class FunctionWithDefaultArgumentsClass {

    fun defaultParamsFunction(funcParam1: String, funcParam2: Int = 30): String {
        return "def"
    }
}

fun functionWithDefaultArgumentsExample() {
    // funcParam2 will be the default parameter
    FunctionWithDefaultArgumentsClass().defaultParamsFunction(funcParam1 = "1")
}

After switching to Swift, this feature disappears, and all arguments must be specified when calling the function:

FunctionWithDefaultArgumentsClass().defaultParamsFunction(funcParam1: "1", funcParam2: 100)

SKIE

The recommended approach is to enable default argument interop using an annotation on individual functions where necessary.

class FunctionWithDefaultArgumentsClass(val arg1: Int = 1) {

    @DefaultArgumentInterop.Enabled
    fun functionWithDefaultArgument(arg2: Int = 2) {
        println(arg2)
    }

}

This will allow specifying only a subset of the arguments when calling the function.

let defaultArguments = FunctionWithDefaultArgumentsClass(arg1: 123)
defaultArguments.functionWithDefaultArgument()

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