Expected BEGIN_OBJECT but was BEGIN_ARRAY" using Gson in Kotlin

Question

I'm trying to retrieve data from an api. The JSON response looks like this


{
    "result":"success",
    "documentation":"https://www.exchangerate-api.com/docs",
    "terms_of_use":"https://www.exchangerate-api.com/terms"
    "supported_codes":[
        ["AED","UAE Dirham"],
        ["AFN","Afghan Afghani"],
        ["ALL","Albanian Lek"],
        ["AMD","Armenian Dram"],
        ["ANG","Netherlands Antillian Guilder"],
        ["AOA","Angolan Kwanza"],
        ["ARS","Argentine Peso"],
        ["AUD","Australian Dollar"],
        ["AWG","Aruban Florin"],
        ["AZN","Azerbaijani Manat"],
        ["BAM","Bosnia and Herzegovina Convertible Mark"],
        ["BBD","Barbados Dollar"] etc. etc.
    ]
}

And this is the dataclass I have for it.

CurrencyResponse.kt


package com.example.currencyconverter.data

import com.squareup.moshi.Json

data class CurrencyResponse(
    @Json(name="supported_codes") var supported_codes: List<Codes>
) {
    data class Codes(
        @Json(name="0") var currency_code: String
    ) {

    }

}

Yet I'm still getting the error mentioned in the title. Any help is greatly appreciated

I'm not very familiar with Gson, but it doesn't seem right that you deserialize array (e.g. ["AED","UAE Dirham"]) to Codes object. You probably need something like this: var supported_codes: List<List<String>> or maybe use a custom serializer. — broot
– broot, Commented Oct 25, 2021 at 21:52

Putra Nugraha · Accepted Answer · 2021-10-26 02:01:53Z

0

If possible, I think the API response scheme need a little modification. I think the supported_codes should contains list of object instead, i.e.

    "supported_codes":[
        {
             "currency_code": "AED",
             "currency_name": "UAE Dirham"
        },
        {
             "currency_code": "AFN",
             "currency_name": "Afghan Afghani"
        },
        ... etc ...
    ]

Then, in your kotlin code, you need to modify the Codes data class to:

data class Codes(
   @Json(name="currency_code") val currencyCode: String,
   @Json(name="currency_name") val currencyName: String,
)

answered Oct 26, 2021 at 2:01

Putra Nugraha

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4 Comments

Ahmadddd4 Over a year ago

But here's the thing, the array entries don't have a name so can I write "currency_code" and "currency_name" as names?

Putra Nugraha Over a year ago

Unfortunately, it requires to change the API response schema as well. But, in my opinion, putting array of object inside supported_codes can help to ease the client side to identify the property passed, instead array of array

Ahmadddd4 Over a year ago

I changed it to this ` data class CurrencyResponse( @Json(name ="supported_codes") val supportedCodes: List<List<String>> ){ } ` The app no longer crashes but I'm getting a null response

Putra Nugraha Over a year ago

Or, you can try to parse supportedCodes as answered in stackoverflow.com/a/17974337

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