[Solved] JSON Deserialization Assistance Request

Unity Engine
1

Hello out there! :slight_smile: I’m working on coding an in-game message system for a Facebook game and am having some difficulties wrapping my head around deserializing the JSON information I’m getting back. The example code provided by Facebook seemed like a good jumping off point, but I must be going wrong somewhere because I’m getting an error stating that I “cannot cast from source type to destination type”. I’ve been up for about a day and a half now, so I may just be missing something incredibly obvious, but since I’m new to handling JSON at all, I thought I’d ask. (If you’ve got links to any good tutorials, I’d love to see them!)

Here’s an example of the JSON info:

{
  "data": [
    {
      "application": {
        "category": "Games",
        "link": "https:\/\/www.facebook.com\/game-name-here\/",
        "name": "Example Game",
        "namespace": "example-game",
        "id": "000000000000000"
      },
      "created_time": "2015-08-17T14:49:28+0000",
      "from": {
        "name": "Player One",
        "id": "1111111111111111"
      },
      "message": "Player One sent you a life!",
      "to": {
        "name": "Player Two",
        "id": "22222222222222222"
      },
      "id": "333333333333333_44444444444444444"
    }
  ]
}

And here’s my deserializition code, extracted from the full script for example purposes:

using Facebook;
using Facebook.MiniJSON;

public class FBManager : MonoBehaviour
{
    public void CheckMessages(FBResult result)
    {
        if(result.Error != null)
        {
            Debug.LogError("Error retrieving messages from Facebook.");
        }
        else
        {
            Debug.LogError("Checking messages: " + result.Text);
            var responseObject = Json.Deserialize(result.Text) as Dictionary<string, object>;
            object messagesH;
            var messages = new List<object>();
            if (responseObject.TryGetValue("data", out messagesH))
            {
                messages = (List<object>)(((Dictionary<string, object>)messagesH)["data"]);
                if(messages.Count > 0)
                {
                    var msgDict = ((Dictionary<string,object>)(messages[0]));
                    var msg = new Dictionary<string, string>();
                    msg["from"] = (string)msgDict["from"];
                    msg["message"] = (string)msgDict["message"];
                    Debug.LogError("Message from " + msg["from"] + ": " + msg["message"]);
                }
            }
        }
    }
}

The “cannot cast” error seems to be coming from this line:

messages = (List<object>)(((Dictionary<string, object>)messagesH)["data"]);

For reference, here’s a link to the Facebook example:

I’ll keep poking and prodding at it, but would certainly appreciate any pointers & assistance. Thanks!

2

Personally, I would recommend you to try out JSON Object:

So far I have been most pleased with it and seems to have good performance.

That way you can try the following:

public void CheckMessages(FBResult result)
    {
        if(result.Error != null)
        {
            Debug.LogError("Error retrieving messages from Facebook.");
        }
        else
        {
            Debug.LogError("Checking messages: " + result.Text);
            var jsonObj = new JSONObject( result.Text );
           
            if ( jsonObj.HasField("data") )
            {
                JSONObject data = jsonObj["data"];
                if (data.IsArray)
                {
                     foreach (JSONObject obj in data.list)
                     {
                          string from = obj["from"].str;
                          string message = obj["message"].str;
                          Debug.LogError("Message from " + from + ": " + message);
                     }
                }
           }
    }

Hope it helps! (and hope it works, haven’t tested the code o_o")

1 Like
3

Thanks, Fajlworks! I’ll take a look :slight_smile: Anything that can simplify an otherwise messy process is fine by me, and you can’t beat the price, haha.

1 Like
4

It works wonderfully! I need to figure out how to get the “name” out of the “from” info now, but I’m sure I can work it out with a bit of fiddling. Thanks again :slight_smile:

5

I’d try:

string name = obj["from"]["name"].str;

Hopefully it works :slight_smile:

2 Likes
6

Oh wow, I’d never have guessed it would be that easy. You’re a lifesaver! Thanks again, ever, ever so much. With that headache out of the way, I’m ready to rock 'n roll! :stuck_out_tongue: