Hi, I have two separate questions on Polymorphic S...

# serialization

[Zhiqiang Bian]

Hi, I have two separate questions on Polymorphic Serializer.
• line 36 : Is it possible to set JsonContentPolymorphicSerializer for an abstract class programatically in run time? Something looks like

AbstractRelationship.serializer = if (flag == 1) polySerializer1 else polySerializer2

• I am deserialising AbstractRelationship based on the JsonElement inside. Is it possible to make polymorphic based on the map key on line 32 , maybe with Contextual Serializer or Map Serializer?

[Emil Kantis]

To me it looks like you have an entity that contains either a single reference, or a list of references? Like :

{
  "name": "John"
  "address": "my address"
}

{
  "name": "Emmanouil",
  "address": ["addr1", "addr2"]
}

If so, you could use a JsonTransformingSerializer to always wrap potential single elements before delegating to a generated serializer for

@Serializable
data class Person(val name: String, val address: List<String>)

[Emil Kantis]

Something like..

object PersonSerializer : JsonTransformingSerializer<Person>(Person.serializer()) {

   override fun transformDeserialize(element: JsonElement): JsonElement {
      if (element !is JsonObject) return element
      return JsonObject(
         element.jsonObject.entries.associate { (key, value) ->
            if (key == "address" && value !is JsonArray) key to JsonArray(listOf(value)) 
            else key to value
         }
      )
   }
}

[Zhiqiang Bian]

My use case is like having a dynamic PolyphomicSerializer. Assume there are two different class, User and organisation , need to be deserialised into.

"User": {
    "data": {
        "address": [addr1, addr2] => ResourceLink
    }
}

"Organisation": {
    "data": {
        "address": addr3 => ResourceLink
    }
}

And my data model is like

class User(val address: List<Address>)
class Organisation(val address: Address)

You told me about JsonTransformingSerializer a few days ago, and it is a good workaround for me. (And thank you for answering my question again🙏). I just need to turn the address of organisation into a list with one item inside.

Now, I am trying to find out if I can preserve the difference of T and List<T> in my models.

[Zhiqiang Bian]

So, setting JsonContentPolymorphicSerializer dynamically in run-time would be the ideal solution for me (if it is doable).
Alternatively, I can just keep using my current SingleItemList Strategy, which also works but not ideal, because it twists the models.