Accessing data inside JSON Array with C#

Question

I am writing a C# script in unity to get the weather of the location the player is in. I am almost done, all I have to do is extract the data from the JSON file the weather API returned. I am using SimpleJSON to read and extract the JSON. The JSON looks something like this:

{
  "coord": {
    "lon": (floating point number),
    "lat": (floating point number)
  },
  "weather": [
    {
      "id": 804,
      "main": "Clouds",
      "description": "overcast clouds",
      "icon": "04n"
    }
  ],
  "base": "stations",
  "main": {
    "temp": 292.01,
    "feels_like": 292.12,
    "temp_min": 291.15,
    "temp_max": 293.15,
    "pressure": 1018,
    "humidity": 72
  },
  "visibility": 9000,
  "wind": {
    "speed": 1.5,
    "deg": 130
  },
  "clouds": {
    "all": 100
  },
  "dt": 1594239812,
  "sys": {
    "type": 1,
    "id": 1308,
    "country": "COUNTRY-CODE",
    "sunrise": 1594178675,
    "sunset": 1594235893
  },
  "timezone": 7200,
  "id": 2954172,
  "name": "CITY",
  "cod": 200
}

I need to access the "description" in the "weather" array. However I could not figure out how to get it to work. This is my C# code:

var PARSED_JSON_2 = JSON.Parse(JSON_DATA_2);
var weather_description = PARSED_JSON_2["weather"][2]; //returns null
//I also tried something like this:
var weather_description = PARSED_JSON_2["weather"]["description"][2]; //returns null
var weather_description = PARSED_JSON_2["weather"]["description"][2].Value; //Returns nothing.

A Debug.Log would show an empty string.

I tried to follow this reference here: http://wiki.unity3d.com/index.php/SimpleJSON

(In a nutshell I need to access an element inside of a JSON array, but I can't figure out how to. Any help is appreciated.)

needs to be done with SimpleJSON? or could you use any other third party library? — Lotan
– Lotan, Commented Jul 9, 2020 at 12:45
I am on linux, so my options aren't as abundant. I found SimpleJSON to work best up until this point, but if you have suggestion, I would try it aswell. As long as I can figure out how to access the element "description" inside the "weather" array of the json file. — a coder
– a coder, Commented Jul 9, 2020 at 12:46
you can create C# Class and deserialize it to C# object. You can update field as per your wish — Shyam sundar shah
– Shyam sundar shah, Commented Jul 9, 2020 at 12:48
I'll suggest to use Newtonsoft (I don't know if it works on linux or not), or you can use my JsonManager (github.com/EricBatlle/SimpleUnityUtils/tree/master/Assets/…) — Lotan
– Lotan, Commented Jul 9, 2020 at 12:48
@Lotan is it cross platform / does it work with unity? I am aiming to make this cross platform, mainly targeting mobile devices. Oh, lol. I take that back - Just saw the using UnityEngine; — a coder
– a coder, Commented Jul 9, 2020 at 12:51

derHugo · Accepted Answer · 2020-07-09 13:35:27Z

You are trying to access an index 2 that does not exist. There is only one single element in the weather array. In this case that SimpleJSON library simply returns null instead of throwing a proper exception!

You should rather use the index 0

var weather_description = PARSED_JSON_2["weather"][0];

In general you could also use the JsonUtility and deserialize your complete array into a proper c# class representation. Then you would immediately see how many elements the array/s has/have or get the expected exceptions properly.

Yours would look like

[Serializable]
public class Root
{
    public Coord coord;
    public Weather[] weather;
    public string @base;
    public Main main;
    public int visibility;
    public Wind wind;
    public Clouds clouds;
    public double dt;
    public Sys sys;
    public int timezone;
    public int id;
    public string name;
    public int cod;
}

[Serializable]
public class Coord
{
    public float lon;
    public float lat;
}

[Serializable]
public class Weather
{
    public int id;
    public string main;
    public string description;
    public string icon;
}

[Serializable]
public class Main
{
    public float temp;
    public float feels_like;
    public float temp_min;
    public float temp_max;
    public float pressure;
    public float humidity;
}

[Serializable]
public class Wind
{
    public float speed;
    public float deg;
}

[Serializable]
public class Clouds
{
    public int all;
}

[Serializable]
public class Sys
{
    public int type;
    public int id;
    public string country;
    public int sunrise;
    public int sunset;
}

And then you would do e.g.

var root = JsonUtility.FromJson<Root>(JSON_DATA_2);
var weather = root.weather[0];

The big advantage of this approach would be that you can also directly see the result in the Inspector of Unity by writing into a

public class JsonTester : MonoBehaviour
{
    [Header("Input")]
    [Tooltip("Copy your json string here and call \"Test\" from the Context menu")]
    [SerializeField] [TextArea] private string _testJson;

    [Header("Output")]
    [SerializeField] private Root _receivedJson;

    [ContextMenu(nameof(Test))]
    private void Test()
    {
        VisualizeJson(_testJson);
    }

    public void VisualizeJson(string json)
        JsonUtility.FromJsonOverwrite(json, _receivedJson);
    }
}

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