Optionals/Nullables with Kotlin native and ObjectiveC/Swift

Question

I have a kotlin function returning a Nullable like the following:

fun getBoolOrNil(): Boolean? {
    if (something){
        return true
    }
    return null
}

I then crosscompile this with kotlin native to objectiveC for iOs, but the method in the resulting Library that I use with objC/swift returns

__attribute__((swift_name("KotlinBoolean")))
@interface MyLibBoolean : MyLibNumber
- (instancetype)initWithBool:(BOOL)value;
+ (instancetype)numberWithBool:(BOOL)value;
@end;

whilst a MyLibNumber is just a

@interface MyLibNumber : NSNumber
...

Is this the crosscompilers try to give me something I can use like an Optional/Nullable or is this Object unusable for that purpose? I know that ObjectiveC does not support Optionals/Nullables, but I do not understand this Object that the Crosscompiler gives me here.

Answer 1

The closest your function translates to Objective C is something like:

- (NSNumber * _Nullable)getBoolOrNil {
    if(something) {
        return [NSNumber numberWithBool:YES];
    }
    return NULL;
}

The usage of NSNumber with initWithBool is a common pattern of expressing the nullable boolean in Objective-C. So that's what your cross-compiler did, except it also created a wrapper for NSNumber, and now the same function at the top, could be expressed as:

- (MyLibBoolean * _Nullable)getBoolOrNil {
    if(something) {
        return [MyLibBoolean numberWithBool:YES];
    }
    return NULL;
}

Of course in Swift, this whole wrapping is not needed, the function would look almost exactly the same as in kotlin:

func getBoolOrNil() -> Bool? {
    if something {
        return true
    }
    return nil
}