Declare classes in Kotlin functions

Asked Jan 25 '21 at 09:56

Active Jan 25 '21 at 09:56

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I declared a data class in a Kotlin function, but the data is empty after gson conversion.

fun writeAndFlush(context: StateMachine) {
        data class Temp(val model: TaskModel, val totalTime: String?, val state: String)

        val temp = Temp(context.businessObj, context.totalTime, context.state.toString())

        Log.e("test", temp.toString()) // print data here.

        val json = Gson().toJson(temp)

        Log.e("test", json) // problem here.....print null
    }

Is there any problem with this way?

asked Jan 25 '21 at 09:56

Shine Lee

1

what's the purpose of declaring a class inside of a function? – Nicola Gallazzi Jan 25 '21 at 11:17
The problem is not the class inside the function, but inside the line `val json = Gson().toJson(temp)` . Debug it and see why it is parsed badly. – Neo Jan 25 '21 at 13:14
The language lets you do it for encapsulation, but evidently Gson can't handle that, maybe. – Tenfour04 Jan 25 '21 at 13:44
The problem is with Gson not supporting serialization of local classes. See: https://stackoverflow.com/questions/15039670/can-i-use-gson-to-serialize-method-local-classes-and-anonymous-classes – Mafor Jan 25 '21 at 15:25
@NicolaGallazzi emmm, just a spark....:) – Shine Lee Jan 26 '21 at 01:47
@Neo Yep, It's a problem with Gson serialization. Jackson And Moshi will be ok. – Shine Lee Jan 26 '21 at 02:05
@Tenfour04 Yes, Gson can't handle this. The classes in the method is also considered as an anonymous inner class....so... – Shine Lee Jan 26 '21 at 02:10
@Mafor Thx, you helped me a lot.. – Shine Lee Jan 26 '21 at 02:11

Declare classes in Kotlin functions

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