Hi all, I've been trying to call a method that takes a nullable Int in Kotlin common code from Swift...

# multiplatform

[Neal Sanche]

Hi all, I've been trying to call a method that takes a nullable Int in Kotlin common code from Swift. The method signature is:

suspend fun getEpisodes(page: Int?): EpisodePage

On the Swift side, have been try to write code but always am told:

Cannot convert value of type 'Int32' to expected argument type 'KotlinInt?'

This confuses me, and I'm sure there's a simple explanation. I can change the function signature to getEpisodes(page: Int = 1) instead, and that's much easier to deal with. So I'm curious what's going on here?

[Neal Sanche]

I've been thinking it's doing something to box up the Int? because native ints can't be null. I guess I'd love to see a nice example of how to work with this on the Swift side.

[Barco]

It needs to be cast to NSNumber

[Barco]

https://kotlinlang.org/docs/reference/native/objc_interop.html#nsnumber

[Barco]

There is a link to an example there

[Neal Sanche]

My Swift is not so good, admittedly, but this is not working for me.

[Barco]

What does the suggested fix do?

[Neal Sanche]

Crashes with

Could not cast value of type '__NSCFNumber' (0x7fff86d65440) to 'SharedInt' (0x10df11200).

[Neal Sanche]

Okay, getting closer here.

[Neal Sanche]

class EpisodeViewModel: ObservableObject {
    @Published public var episodes: [Episode] = []
    let repository = TestRepository()
    var nextPage: NSNumber? = nil
    
    func fetchEpisodes() {
        repository.getEpisodes(page: (self.nextPage as? KotlinInt)) { (data, error) in
            if let newEpisodes = data?.episodes {
                self.episodes.append(contentsOf: newEpisodes)
            }
            self.nextPage = data?.nextPage
        }
    }
    
    public var shouldDisplayNextPage: Bool {
        return nextPage != nil
    }
}

[Barco]

How about just using the constructor of KotlinInt? KotlinInt(self.nextPage!)

[Neal Sanche]

The above code works now. I guess it's just my own learning how things are being mapped. Thanks for the help though, @Barco

[Barco]

I think we both learned something 🙂