how to handle two different Retrofit response in Kotlin?

Question

I have tried to read this similar thread in java in here so I try the accepted answer there but it doesn't work. here is my problem

I will get two different JSON Response from an endpoint. if I successfully get the Restaurant data, the JSON will be like this

{

    "R": {
       "has_menu_status": {
       "delivery": -1,
       "takeaway": -1
        },
       "res_id": 18941862,
       "is_grocery_store": false
    },
    "id": "18941862",
    "name": "Pizza Maru",
    "url": "https://www.zomato.com/jakarta/pizza-maru-1-thamrin?utm_source=api_basic_user&utm_medium=api&utm_campaign=v2.1",
    "location": {
        "address": "Grand Indonesia Mall, East Mall, Lantai 3A, Jl. M.H. Thamrin No. 1, Thamrin, Jakarta",
        "locality": "Grand Indonesia Mall, Thamrin",
        "city": "Jakarta",
        "city_id": 74,
        "latitude": "-6.1955810000",
        "longitude": "106.8213770000",
        "zipcode": "",
        "country_id": 94,
        "locality_verbose": "Grand Indonesia Mall, Thamrin, Jakarta"
    },
    "switch_to_order_menu": 0,
    "cuisines": "Pizza",
    "timings": "10 AM to 10 PM",
    "average_cost_for_two": 180000,
    "price_range": 3,
    "currency": "IDR",
    "thumb": "https://b.zmtcdn.com/data/pictures/chains/2/18941862/403aa36cb046e86a694e7989bb7cd545.jpg?fit=around%7C200%3A200&crop=200%3A200%3B%2A%2C%2A",
    "has_online_delivery": 0,
    "is_delivering_now": 0,
    "store_type": "",
    "phone_numbers": "021 3108656",
    
}

then If I send invalid restaurantID then I will get error JSON Response like this:

{
    "code": 404,
    "status": "Not Found",
    "message": "Not Found"
}

here is the data class I made

data class Restaurant (

    @SerializedName("id")
    val id : Int = 0,

    @SerializedName("name")
    var name : String = "",

    @SerializedName("url")
    val url : String = "",

    @SerializedName("location")
    val location : Location = Location(),

    @SerializedName("currency")
    val currency : String = "",

    @SerializedName("phone_numbers")
    val phone_numbers : String = "",

    @SerializedName("thumb")
    val thumbnail : String = ""

)

for successful Response

data class Location (

    @SerializedName("address")
    val address : String = "",

    @SerializedName("city")
    val city : String = "",

    @SerializedName("latitude")
    val latitude : Double = 0.0,

    @SerializedName("longitude")
    val longitude : Double = 0.0,

    @SerializedName("zipcode")
    val zipcode : String = ""

)
    

for Error Response

data class ErrorResponse (

    val code : Int,
    val status : String,
    val message : String
)
         

here is my Interface for my Retrofit. the idea is, I will cast it as Any first, then I will downcast either to Restaurant or ZomatoErrorResponse

interface RestaurantAPI {

    @Headers("user-key: $USER_KEY_ZOMATO")
    @GET("restaurant")
    fun getRestaurantDetail(
        @Query("res_id") id: Int
    ): Call<Any>
}

here is the error:

so I use my retrofit like this

        val call = restaurantService.getRestaurantDetail(restaurantID)

        call.enqueue(object: Callback<Any>{

            override fun onResponse(call: Call<Any>, response: Response<Any>) {

                if (response.isSuccessful) {

                    // this line is executed

                    Log.d("checkxxx","${response.body()}")

                    val restaurantData = response.body() as Restaurant // <-- but Error while casting Any to Restaurant in here
                    restaurant.postValue(restaurantData)
                } 
                
            }


        })

my app crash at that line. but actually I can successfully get the data, but I fail to cast it to Restaurant.

here the logcat of my response.body()

what went wrong in here ?

or maybe there is a better approach than this one

Answer 1

I finally can solve my problem using this code below

        val call = restaurantService.getRestaurantDetail(restaurantID)

        call.enqueue(object: Callback<Any>{

            override fun onResponse(call: Call<Any>, response: Response<Any>) {


                if (response.isSuccessful) {


                    val gson = Gson()
                    val restaurantData = gson.fromJson(gson.toJson(response.body()), Restaurant::class.java)
                    

                } else {

                    val errorBody = response.errorBody() ?: return
                    val type = object : TypeToken<ErrorResponse>() {}.type
                    val errorResponse: ErrorResponse? = gson.fromJson(errorBody.charStream(), type)
                    val errorMessage = errorResponse?.message ?: "Unknown Error"

                    

                }
            }


        })

don't forget to set the interface to be Any like this

interface RestaurantAPI {

    @Headers("user-key: $USER_KEY_ZOMATO")
    @GET("restaurant")
    fun getRestaurantDetail(
        @Query("res_id") id: Int
    ): Call<Any> // <---- set to Any like this
}

in my case, I have successful response and an error response. so I need to separate it like that.

but if you have 2 successful responses but it has different JSON then you need to perform null checking to restaurantData in my code above, if null then mapping it the other POJO.

Answer 2

You should use gson to convert json to an object https://github.com/google/gson

Example 
val gson = Gson();
val  jsonInString = "{\"userId\":\"1\",\"userName\":\"Yasir\"}";
val user = gson.fromJson(jsonInString, User.class);