Save load custom class values not assigned object null reference

Questions & Answers
1

Okay, so in short, this is my first time trying to create save file codes and custom classes in unity, and the guides I am following does not provide all the data I need to figure out how to continue.

What I am trying to do is to, simply put, press a gui button, and that should set some variables from a custom script to a hard-coded value (this is just for testing, the values are meant to be some form of user input, either buttons or a text field) and save these values. Now, when I press my gui button, I get the error “reference Null Reference Exception: Object reference not set to an instance of an object”.

I am probably doing a whole world of hurt with errors I cannot see here but this is the lines of code that unity points out as problems:

DemographicData.Completed.TD.Age = 20;
DemographicData.Completed.TD.Gender = “Kvinde”;
DemographicData.Completed.TD.AlreadyCompletedThis = true;

If I outcomment those three lines, unity stop complaining.

And this is the relevant code pieces:

Custom class script 1)

using UnityEngine;
using System.Collections;

[System.Serializable]
public class TestData{

	public bool AlreadyCompletedThis;
	public int Age;
	public string Gender;

	public TestData(){
		this.Age = 0;
		this.Gender = "";
		this.AlreadyCompletedThis = false;
	}
}

Custom class 2

[System.Serializable]
public class DemographicData{
	public static DemographicData Completed;
	public TestData TD;
	public DemographicData(){
		TD = new TestData ();
	}
}

The relevant code from the GUI script

if (GUI.Button (new Rect ((Screen.width * 0.5f) - (SWdNoB * 3f * 0.5f), (Screen.height * 0.5f), SWdNoB * 3f, BoxHeight), "I'm filling out data")) {
	DemographicData.Completed.TD.Age = 20;
	DemographicData.Completed.TD.Gender = "Male";
	DemographicData.Completed.TD.AlreadyCompletedThis = true;
	SaveLoad.SaveTestData ();
	ContinueOnToMenu = true;
}

The not so relevant save script, but just in case something is wrong here

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<DemographicData> GameTestData = new List<DemographicData>();
	public static void SaveTestData(){
		SaveLoad.GameTestData.Add (DemographicData.Completed);
		BinaryFormatter bf = new BinaryFormatter ();
		FileStream file = File.Create (Application.persistentDataPath + "/GameTestData.gd");
		bf.Serialize (file, SaveLoad.GameTestData);
		file.Close ();
	}
	public static void LoadTestData (){
		if (File.Exists (Application.persistentDataPath + "/GameTestData.gd")) {
			BinaryFormatter bf = new BinaryFormatter ();
			FileStream file = File.Open (Application.persistentDataPath + "/GameTestData", FileMode.Open);
			SaveLoad.GameTestData = (List<DemographicData>)bf.Deserialize (file);
			file.Close ();
	}
}

}

If it matters anything, The custom class “DemographicDate” is placed in the SaveLoad script, although it has been placed outisde everything.

I hope this is enough information to get the help I need, I normally love to figure these things out for myself, but I am lacking the time to do so.

Thanks in advance :slight_smile:

2

So I foudn out that I called my list before I created it, and that I did not create the lists I though I was creating.

I solved the problem by putting a statement into the load function telling it that if there were no list, then create one, and in the gui script, I called the load function before trying to stuff things into it.

If someone somehow get the same error, this is my now changed code:

Custom class 1

(the same)

custom class 2

[System.Serializable]
public class DemographicData{
	*(deleted line)*
	public TestData TD;
	public DemographicData(){
		TD = new TestData ();
	}
}

Gui script code

void OnGUI () {

	/*(...)*/

		if (!StartWasPressed) {
			if (GUI.Button (new Rect (/*...*/), "Start")) {
				SaveLoad.LoadTestData (); /*(This is where I make a list if there is none)*/
				StartWasPressed = true;
			}
		}
		if (StartWasPressed) {
			ContinueOnToMenu = SaveLoad.GameTestData [0].TD.AlreadyCompletedThis;
			if (GUI.Button (new Rect (...), "Quit")) {
				Application.Quit ();
			}
			if (!ContinueOnToMenu) {

				if (DemographicsDataFilledOut [0]) { //age, gender, occupation
					//age
					GUI.Box(new Rect(/*...*/), "Please select your

age range");
if (GUI.Button(new Rect(…)," - 15")){
/(…)/
SaveLoad.GameTestData [0].TD.Age = 1;
DataFieldMarkedCorrectly [0] = true;
}

					/*(...)*/

					if (GUI.Button (new Rect (/*...*/),"Continue")) {
						if (/*all data filled out == true*/) {
							SaveLoad.SaveTestData ();
							DemographicsDataFilledOut [0] = false;
							DemographicsDataFilledOut [1] = true;
						}
					}

					/*(...)*/
				}
				/*(...)*/
			}

and the now very relevant save load script

using UnityEngine;
using System.Collections;
using System.Collections.Generic; //This allows for dynamic lists
using System.Runtime.Serialization.Formatters.Binary;
using System.IO;

public static class SaveLoad {

	public static List<DemographicData> GameTestData = new List<DemographicData>();
	public static void SaveTestData(){
		BinaryFormatter bf = new BinaryFormatter ();
		FileStream file = File.Create (Application.persistentDataPath + "/GameTestData.gd");
		bf.Serialize (file, SaveLoad.GameTestData);
		file.Close ();
	}
	public static void LoadTestData (){
		if (File.Exists (Application.persistentDataPath + "/GameTestData.gd")) {
			BinaryFormatter bf = new BinaryFormatter ();
			FileStream file = File.Open (Application.persistentDataPath + "/GameTestData.gd", FileMode.Open);
			SaveLoad.GameTestData = (List<DemographicData>)bf.Deserialize (file);
			file.Close ();
		} else { /*(This is where I make sure that a new list is created upon load call)*/
			SaveLoad.GameTestData.Add (new DemographicData());
		}
	}

Hopes this helps someone in the future.