OptionalStringTernaryFunction
class OptionalStringTernaryFunction<A, OA : ObservableValue<A>, B, OB : ObservableValue<B>, C, OC : ObservableValue<C>>(argA: OA, argB: OB, argC: OC, lambda: (A, B, C) -> String?) : TernaryFunction<String?, A, OA, B, OB, C, OC> , ObservableOptionalString
Boilerplate which avoids having to use generics.
Similar to StringTernaryFunction, but the value can also be null.