class StringConverter : JsonSerializer<String?>,

     JsonDeserializer<String?> {

     override fun serialize(

         src: String?, typeOfSrc: Type?,

         context: JsonSerializationContext?

     ): JsonElement {

         return if (src == null) {

             JsonPrimitive("")

         } else {

             JsonPrimitive(src.toString())

         }

     }

     @Throws(JsonParseException::class)

     override fun deserialize(

         json: JsonElement, typeOfT: Type?,

         context: JsonDeserializationContext?

     ): String {

         return json.asJsonPrimitive.asString

     }

 }

     fun parseDevices(array : JsonArray){

         val gson = GsonBuilder().run {

             registerTypeAdapter(String::class.java, StringConverter())

             create()

         }

         for (je in array){

             val obj = je.asJsonObject

             if(!obj.has("type")) continue

             val type = obj.get("type").asInt

             when(type){

                  -> {

                     val ward = gson.fromJson(je,Wardship::class.java)

                     ...

                 }

                 //...

             }

         }

     }