Is there a reason why Unity would be able to read one variable in a script and not another?

Questions & Answers
1

I have a single script attached to a gamemanager object in my game that has two sections: one as a GameManager that holds data between scenes and one as a Serializable section which converts the data from the GameManager to enable the Save function to save it.

If I play the game through from scene 1 - scene 3 and then save, the variables are all successfully read by my Save function (in a separate script). If, however, I load a previous game, I run into problems. The data is successfully loaded into the game and I can play it (ie. the GameManager.control.xxxx variables successfully use the loaded data), but when I go to save again, I can’t because the game cannot find the Serializable section (PlayerData.current.xxxx). ie. Unity says object reference is not set to an object for the following line of the Save function:

   Debug.Log ("Saved Data: " + PlayerData.current.healthpotion);

This is despite the fact it’s already accessed it to make the original save file. Is there any reason why a game wouldn’t be able to see another section of the same script?

Main script

using UnityEngine;
using System.Collections;

public class GameManager : MonoBehaviour {

	public static GameManager control;

	//recording names
	public string username;

	//setting up potion score
	public int hlthpotion;
	public int mnpotion;

....

[System.Serializable]
public class PlayerData {
	public static PlayerData current;
	public string UserName;
	public int healthpotion;
	public int manapotion;
	public bool redWizard;
	public bool purpleWizard;
	public bool blueWizard;


	public PlayerData () {
		UserName = GameManager.control.username;
		redWizard = GameManager.control.redwizard;
		blueWizard = GameManager.control.bluewizard;
		purpleWizard = GameManager.control.purplewizard;
		healthpotion = GameManager.control.hlthpotion;
		manapotion = GameManager.control.mnpotion;

	}
}

Loading/Saving script

    using UnityEngine;
    using System.Collections;
    using System.Collections.Generic;
    using System.Runtime.Serialization.Formatters.Binary;
    using System.IO;
    
    public static class SaveLoad {
    
    	public static List<PlayerData> savedGames = new List<PlayerData> ();
    
    	public static void Save () {
    		Debug.Log ("Original Data: " + GameManager.control.hlthpotion);
    		Debug.Log ("Saved Data: " + PlayerData.current.healthpotion);
    		PlayerData.current.healthpotion = GameManager.control.hlthpotion;
    		PlayerData.current.manapotion = GameManager.control.mnpotion;
    		Debug.Log ("Game To Be Saved");
    		Debug.Log ("Original Data" + GameManager.control.hlthpotion);
    		Debug.Log ("Saved Data" + PlayerData.current.healthpotion);
    		SaveLoad.savedGames.Add (PlayerData.current);
    		Debug.Log ("Game Added");
    		BinaryFormatter bf = new BinaryFormatter ();
    		FileStream file = File.Create (Application.persistentDataPath + "/playerInfo.dat");
    		bf.Serialize (file, SaveLoad.savedGames);
    		file.Close ();
    		Debug.Log ("Game Saved " + PlayerData.current.UserName);
    	}

     public static void Load() {
		if (File.Exists (Application.persistentDataPath + "/playerInfo.dat")) {
			Debug.Log ("Save File exists");
			BinaryFormatter bf = new BinaryFormatter ();
			FileStream file = File.Open (Application.persistentDataPath + "/playerInfo.dat", FileMode.Open);
//			SaveLoad.savedGames = (List<PlayerData>)bf.Deserialize (file);
			List<PlayerData> playerDataList = (List<PlayerData>)bf.Deserialize (file);
			file.Close ();
			Debug.Log ("Save File Closed");
			foreach (PlayerData Pd in playerDataList) {	
				GameManager.control.username = Pd.UserName;
				Debug.Log ("Username matched");
				GameManager.control.redwizard = Pd.redWizard;
				Debug.Log ("Red matched");
				GameManager.control.bluewizard = Pd.blueWizard;
				Debug.Log ("Blue matched");
				GameManager.control.purplewizard = Pd.purpleWizard;
				Debug.Log ("Purple matched");
				GameManager.control.hlthpotion = Pd.healthpotion;
				Debug.Log ("Health Potion = " + GameManager.control.hlthpotion);
				GameManager.control.mnpotion = Pd.manapotion;
	//			Debug.Log ("Mana Potion: " + PlayerData.current.manapotion);
			}

		}
	}
}
2

It’s because static fields are not serialized. What you can do is instead of having that as a static field in the PlayerData class, put it as a non-static field in the GameManager (which I assume is a singleton?). Then, if you want to keep references, you can just modify the old current variable as such:

public static PlayerData current { get { return GameManager.singleton.playerData; } }

Or something like that. Then all references would work, and it should serialize properly.