CODEWITHSUNDEEP
c#jsonunity-game-engineexceptionargumentexception
Dieter Claessens
Dieter Claessens

Reputation: 129

JsonUtility.FromJson keeps throwing ArgumentException

I am trying to receive data from my backend in my unity project, the data looks like this:

{"subjectid":98,"name":"test23","first_name":"test23","date_of_birth":"1998-02-16","age":23}

I am using the following line to get the data into an object:

PatientBackend patient = JsonUtility.FromJson<PatientBackend>(responseBody);

The object looks like this:

  using System.Collections;
    using System.Collections.Generic;
    using UnityEngine;
    
    [System.Serializable]
    public class PatientBackend : MonoBehaviour
    {
        public int subjectid;
        public string name;
        public string first_name;
        public string date_of_birth;
        public int age;
    
       public PatientBackend(string name, string first_name, string date_of_birth)
        {
            this.name = name;
            this.first_name = first_name;
            this.date_of_birth = date_of_birth;
        }
}

But everytime this is called it thows the following exception:

System.ArgumentException: Cannot deserialize JSON to new instances of type 'PatientBackend.'
  at UnityEngine.JsonUtility.FromJson (System.String json, System.Type type) [0x00056] in <5070e0347dee4c9faba7201166fbed9d>:0 
  at UnityEngine.JsonUtility.FromJson[T] (System.String json) [0x00001] in <5070e0347dee4c9faba7201166fbed9d>:0 
  at DataService+<createPatient>d__8.MoveNext () [0x0021b] in C:\Users\diete\Documents\Stage\bedrijf_CLEAN-CLONE\VRStrokeRehabilitation\Unity\UnityProject\Assets\Scripts\DataService.cs:87 
UnityEngine.Debug:Log(Object)
<createPatient>d__8:MoveNext() (at Assets/Scripts/DataService.cs:90)

Does anyone know why this isn't working?

Upvotes: 1

Views: 1358

Answers (2)

derHugo
derHugo

Reputation: 90862

You can not create instances of MonoBehaviour via the JsonUtility. A MonoBehaviour only makes sense if it is attached to a GameObject.

It is also not allowed that a MonoBehaviour implements a constructor.

Either do not make it a MonoBehaviour at all. And rather use

[System.Serializable]
public class PatientBackend
{
    public int subjectid;
    public string name;
    public string first_name;
    public string date_of_birth;
    public int age;
    
    public PatientBackend(string name, string first_name, string date_of_birth)
    {
        this.name = name;
        this.first_name = first_name;
        this.date_of_birth = date_of_birth;
    }
}

and

var patientBackend = JsonUtility.FromJson<PatientBackend>(jsonString);

Or if you really need this as a MonoBehaviour instead rather use JsonUtility.FromJsonOverwrite in order to only overwrite the fields of an existing instance.

public class PatientBackend : MonoBehaviour
{
    public int subjectid;
    public string name;
    public string first_name;
    public string date_of_birth;
    public int age;
}

and

JsonUtility.FromJsonOverwrite(jsonString, existingpatientBackend);

Upvotes: 1

Connor Stoop
Connor Stoop

Reputation: 1632

PatientBackend should not be a MonoBehaviour. The JsonUtility can only be used for data classes. MonoBehaviours are components which need to be attached to gameobjects. You can't simply "create" an instance, that's why it failed.

see Answers.unity

Upvotes: 1

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