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kotlinlang

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

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

an explicit argumentless constructor or static factory method might help

<@UKWM37KGV>
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

so, it looks like the problem is with data classes

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

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

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

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

<@UKWM37KGV> have you ever instantiated data classes on iOS?

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

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

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

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

In the meantime I solved it with this extra method:

```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)
        }
    }
}```


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

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