Get float from class in a SerializedProperty - unity3d

Question

I am trying to start using sciptable objects as describe in this talk. Here is my code:
Here is my FloatVariable:
using UnityEngine;
[CreateAssetMenu]
public class FloatVariable : ScriptableObject
{
public float value;
}
Here is my FloatReference:
using UnityEngine;
using System;
[Serializable]
public class FloatReference
{
public bool use_constant = true;
public float constant_value;
public FloatVariable variable_value;
public float v
{
get
{
return use_constant ? constant_value : variable_value.value;
}
set
{
if (use_constant) throw new Exception("Cannot assign constant_value");
else variable_value.value = value;
}
}
}
Here is my GameplayManager where I have one FloatReference value:
using UnityEngine;
using UnityEngine.SceneManagement;
using UnityEditor;
using System;
public class GameplayManager : MonoBehaviour
{
public FloatReference pl_orb_mode;
}
Here is my GameplayManagerEditor where I try to get float from FloatVariable class:
using UnityEngine;
using UnityEditor;
using System;
[CustomEditor(typeof(GameplayManager))]
public class GameplayManagerEditor : Editor
{
public override void OnInspectorGUI()
{
base.OnInspectorGUI();
SerializedProperty pl_orb_mode = serializedObject.FindProperty("pl_orb_mode");
SerializedProperty variable = pl_orb_mode.FindPropertyRelative("variable_value");
SerializedProperty the_value = variable.FindPropertyRelative("value");
float test = the_value.floatValue;
Debug.Log(test);
}
}
When I try to get my float test = the_value.floatValue; I get an error:
NullReferenceException: Object reference not set to an instance of an object
GameplayManagerEditor.OnInspectorGUI () (at Assets/Shared/Scripts/Editor/GameplayManagerEditor.cs:18)
So I can get the FloatVariable variable class as a SerializedProperty but I can't get its value property. Why is that so and how to make it work?

Answer 1

Because FloatVariable is inherit from ScriptableObject, so variable_value becomes a reference not a property in SerializedObject.
You have 2 choice.
Don't use ScriptableObject:
[Serializable]
public class FloatVariable
{
public float value;
}
Or edit the reference object:
var so = new SerializedObject(((GameplayManager)target).pl_orb_mode.variable_value);
var the_value = so.FindPropertyRelative("value");
...
so.ApplyModifiedProperties();
Notice that the second way since FloatVariable is a reference object, change on it will change all other objects that refer to it.