Nulls (null)

A null is used to refer to the intentional absence of a value.

While it can be used as a separate type directly, null most commonly used to make an existing type explicitly nullable:

TypeScript

interface Math extends HybridObject<{ … }> {
  a: number | null
}

Swift

class HybridMath: HybridMathSpec {
  var a: Variant_NullType_Double
}

Kotlin

class HybridMath: HybridMathSpec() {
  override var a: Variant_NullType_Double
}

C++

class HybridMath: public HybridMathSpec {
  std::variant<nitro::NullType, double> a;
};

The NullType is a singleton structure in Nitro. To return null to JS:

Swift

func getNull() -> NullType {
  return .null
}

Kotlin

fun getNull(): NullType {
  return NullType.NULL
}

C++

NullType getNull() {
  return nitro::null;
}

Optionals vs null

In the same way that JavaScript distinguishes between an optional type/undefined and null, Nitro also has two separate concepts for the two.

If you simply want to make an existing type optional, use Optionals instead.