parsing json file in unity

Question

I can't parse JSON in Unity. Here is the JSON file:

{
  "play_classic": [
    { "english": "PLAY CLASSIC" },
    { "spanish": "JUEGO CLÁSICO" },
    { "portuguese": "JUEGO CLÁSICO" },
    { "russian": "IGRAT' V KLASSICHESKUYU" }
  ]
}

the structure and code looks like this:

[System.Serializable]
    class Root
    {
        public List<PlayClassicData> play_classic { get; set; }  
    }



[System.Serializable]
    class PlayClassicData
    {

        public string english { get; set; }

        public string spanish { get; set; }

        public string portuguese { get; set; }

        public string russian { get; set; }
    }

the implementation looks like this:

ParseJson class:

 public void Deserialize()
        {
string path = Application.dataPath + "path...";
        
        using (StreamReader r = new StreamReader(path))
        {
            string json = r.ReadToEnd();
            Root classic = JsonUtility.FromJson<Root>(json);
            //Root classic = JsonConvert.DeserializeObject<Root>(json);
            Debug.Log("english:" + classic.play_classic[0].english);
            Debug.Log("spanish:" + classic.play_classic[0].spanish);
       }
}

The code throws an error:

NullReferenceException: Object reference not set to an instance of an object
Assets.Scripts.Infastructure.PARSER.ParseJson.Deserialize () (at Assets/Scripts/Infastructure/PARSER/ParseJson.cs:23)

Answer 1

Your Json does not match your data

public PlayClassicData[] _playClassicData { get; set; } 

Should be:

public List<PlayClassic> play_classic { get; set; }

so classic._playClassicData is probebly null

Edit:

As derHugo pointed out:

Unity's built-in JsonUtility doesn't support properties.. you want to use fields by removing all the {get; set;}

Should be:

public List<PlayClassic> play_classic;

Answer 2

There are two problems here.

1. Wrong Root. It should bepublic List<PlayClassicData> play_classic { get; set; }
2. Indexing. classic._playClassicData[0].spanish is empty. It's the 2nd element that has the spanish value: classic._playClassicData[1].spanish);

Fixed Root:

class Root
{
   public List<PlayClassicData> play_classic { get; set; } 
}

Demo:

var json = File.ReadAllText("example1.json");
var o = JsonSerializer.Deserialize<Root>(json);
Console.WriteLine(o.play_classic[0].english);
Console.WriteLine(o.play_classic[1].spanish);

This prints:

PLAY CLASSIC
JUEGO CLÁSICO

I've used System.Json.Text.JsonSerializer but with JsonConvert.DeserializeObject<Root>(json); the result is the same.

Answer 3

I will assume the Json Is the representation of a traduction in multiple language. and can have multiple sentence/label translated in a return.
And you don't want a class for play_classic and for play_hard, that will hold the same Language properties. Especially not if adding a language force you to add a property in your frontend and in each and every class.

{
    "play_classic": [
        { "english": "PLAY CLASSIC" },
        { "spanish": "JUEGO CLÁSICO" },
        { "portuguese": "JUEGO CLÁSICO" },
        { "russian": "IGRAT' V KLASSICHESKUYU" }
    ],
    "play": [
        { "english": "PLAY" },
        { "spanish": "JUEGO" },
        { "portuguese": "JUEGO" },
        { "russian": "IGRAT'" }
    ],
    "classic": [
        { "english": "CLASSIC" },
        { "spanish": "CLÁSICO" },
        { "portuguese": "CLÁSICO" },
        { "russian": "KLASSICHESKUYU" }
    ]
}

I will choose Dictionary<string, List<Dictionary<string, string>>> as destination object. And will flattern the inner list like : Dictionary<string, Dictionary<string, string>>.
Note: You will have to additionally install/import Newtonsoft .Net JSON into your project since the built-in JsonUtility doesn't support Dictionary. Comment by derHugo, user:7111561

var resultRaw = JsonConvert.DeserializeObject<Dictionary<string, List<Dictionary<string, string>>>>(input);

var resultFlattern = resultRaw.ToDictionary(
                                x => x.Key, 
                                x=> x.Value.SelectMany(trd=> trd)
                                .ToDictionary(kvp=> kvp.Key, kvp=> kvp.Value)
                            );

Usage : given the button play_classic and the langue "portuguese"
Direct access will be as simple as resultFlattern[buttonName][language]

var buttonName="play_classic"; var language= "portuguese";

if(resultFlattern.TryGetValue(buttonName, out Dictionary<string, string>  allTrads))
{
    if(allTrads.TryGetValue(language, out string traduction)){
        Console.WriteLine($"Traduction for button [{buttonName}] in [{language}] is : [{traduction}]") ;
    }
    else{
        Console.WriteLine($"Cant find tanslation for button : [{buttonName}] in [{language}]") ;
    }
}
else{ 
    Console.WriteLine($"Cant find tanslation for button : [{buttonName}]");
}

Demo : https://dotnetfiddle.net/FcxtUp

I will wrap that into a nice helper that load all traductions only once. And give the translation for a given language and button/label. Il will also fire proof it with a default return to Label name when the traduction is not found.

If language is not something easy to cahnge you can faltern the resul one more time and only keep one translation in Dictionary<string, string>. LabelName/Translation