Unit and Nothing.md

Unit and Nothing

The Unit and Nothing types can be used in the same way as in Kotlin: Unit as an object or void, Nothing cannot be created.

Explanations

Let us have a class like this in Kotlin:

class UnitNothing {

    fun unitType(p: Unit) {
    }

    fun nothingType(n: Nothing) {
    }

    fun returnUnit() {
    }

    fun returnNothing(): Nothing {
        throw IllegalStateException()
    }
}

After converting to Swift, we get from types Unit and Nothing types KotlinUnit and KotlinNothing. In this case, you can create an object of the class KotlinUnit, but you cannot create an object of the type KotlinNothing.

let example = UnitNothing()
example.unitType(p: KotlinUnit())
//Doesn't compile - no init() function
//example.nothingType(n: KotlinNothing())
print(example.returnUnit())
//Crashes app - exception
//example.returnNothing()

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