Why I got empty JSON string returned while using setter and getter in the object class in Unity 5.3?

Question

I tried to use the new JSON serialization feature in Unity 5.3, and I wrote the following code by reference the usage example provided On Unity website. The only different part that I made was creating the variables of the object class (FruitItem class in my case) by using setter and getter instead of making them pure public variables. By doing this, I only got a pair of braces without any contents inside. However, if I delete the getter and setter and make the class variables to be pure public variables, I will be able to get the correct result. Can anybody provide any hints to me why that happened? Thanks in advance for your help.

Code that works properly:

using UnityEngine;
using UnityEditor;
using System.Collections;
using System;

public class testJson : MonoBehaviour {


    // Use this for initialization
    void Start () {

        FruitItem myFruit = new FruitItem (){ name = "apple", price = 52, quantity = 53 };

        string jsonString = JsonUtility.ToJson (myFruit);
        Debug.Log (jsonString);

    }



    // Update is called once per frame
    void Update () {

    }
}

[Serializable]
public class FruitItem{

    //using the pure public variables and the output will be:
    //{"name":"apple","quantity":53,"price":52}

    public string name;
    public int quantity;
    public int price;

}

Code that doesn't work properly:

using UnityEngine;
using UnityEditor;
using System.Collections;
using System;

public class testJson : MonoBehaviour {


    // Use this for initialization
    void Start () {

        FruitItem myFruit = new FruitItem (){ name = "apple", price = 52, quantity = 53 };

        string jsonString = JsonUtility.ToJson (myFruit);
        Debug.Log (jsonString);

    }



    // Update is called once per frame
    void Update () {

    }
}

[Serializable]
public class FruitItem{

    //using the pure public variables and the output will be:
    //{}

    public string name{ get; set;}
    public int quantity{ get; set;}
    public int price{ get; set;}

}

Solution

Unity can not serialize properties.

http://docs.unity3d.com/ScriptReference/SerializeField.html

The serialization system used can do the following:

• CAN serialize public nonstatic fields (of serializable types)
• CAN serialize nonpublic nonstatic fields marked with the [SerializeField] attribute.
• CANNOT serialize static fields.
• CANNOT serialize properties.

Your field will only serialize if it is of a type that Unity can serialize:

Serializable types are:

• All classes inheriting from UnityEngine.Object, for example GameObject, Component, MonoBehaviour, Texture2D, AnimationClip.
• All basic data types like int, string, float, bool.
• Some built-in types like Vector2, Vector3, Vector4, Quaternion, Matrix4x4, Color, Rect, LayerMask.
• Arrays of a serializable type
• List of a serializable type
• Enums
• Structs
• List item

EDIT: Only plain classes and structures are supported; classes derived from UnityEngine.Object (such as MonoBehaviour or ScriptableObject) are not.

https://docs.unity3d.com/ScriptReference/JsonUtility.FromJson.html

Comments

[Ares Li]

Thanks for your response and the reference you provided, Mattias. I didn't realize there are limitations for types supported by unity serialization. However, the keyword "[Serializable]" was referenced by "using System". It seems like a .Net stuff. I am wondering if the serialization limitations set on Unity will impact that far. Thanks again.

[tim]

Thanks for your answer

[Brent McFerrin]

I'm not sure this is still accurate. According to the latest documentation: docs.unity3d.com/ScriptReference/JsonUtility.FromJson.html "Only plain classes and structures are supported; classes derived from UnityEngine.Object (such as MonoBehaviour or ScriptableObject) are not." It seems like the first bullet in your list of Serializable types is now incorrect.