Anyone knows why I get this error `init() is unavailable`

# ios

[Daniele B]

Anyone knows why I get this error init() is unavailable

[Nikolay Kasyanov]

there’s no default arguments in Objective-C, meaning your data class constructor can’t be exactly mapped to Swift

[Nikolay Kasyanov]

an explicit argumentless constructor or static factory method might help

[Daniele B]

@Nikolay Kasyanov
weird, so this happens with all data classes?
I have tried to add an argumentless constructor and companion object method, but it still gives me the same error

[Daniele B]

so, it looks like the problem is with data classes

[Daniele B]

class AppState {
    val masterState : MasterState = MasterState()
    val detailState : DetailState = DetailState()
    val showingDetail : Boolean = false
}

this works fine

[Nikolay Kasyanov]

that’s surprising, default arguments are not properly propagated to Obj-C (and consequently Swift) 🤔

[Daniele B]

I just filed an issue:

[Daniele B]

https://youtrack.jetbrains.com/issue/KT-41908

[Nikolay Kasyanov]

I wonder how the actual Obj-C header looks like for both types, I bet JB folks would appreciate this too

[Daniele B]

@Nikolay Kasyanov have you ever instantiated data classes on iOS?

[Nikolay Kasyanov]

yes, in some cases we have companion object helper methods to instantiate them with default arguments

[Nikolay Kasyanov]

then we do AppState.Companion().initial in Swift

[Daniele B]

Is there a reason why you use a companion object helper?

[Nikolay Kasyanov]

haven’t tried using an explicit argumentless constructor so dunno, perhaps this approach might cause overload resolution issues on the Kotlin side 🤔

[Daniele B]

Ok, let's see what they find out

[Daniele B]

In the meantime I solved it with this extra method:

[Daniele B]

data class AppState (
    val masterState : MasterState = MasterState(),
    val detailState : DetailState = DetailState(),
    val showingDetail : Boolean = false,
) {
    companion object {
        fun initState(): AppState {
            return AppState(MasterState(), DetailState(), false)
        }
    }
}

[Nikolay Kasyanov]

I believe you can omit init parameters there to avoid duplicating default values

[Daniele B]

great, it works like this:

[Daniele B]

data class AppState (
    val masterState : MasterState = MasterState(),
    val detailState : DetailState = DetailState(),
    val showingDetail : Boolean = false,
) {
    companion object {
        fun initState(): AppState {
            return AppState()
        }
    }
}

[Daniele B]

thanks!

[Nikolay Kasyanov]

no probs