Access a Variable of an Object from a previous Scene

Questions & Answers
1

So I’m making a game and what I’d like to do is as follows: If you’ve collected all the items, you are being forwarded to an end screen, in which your total score is shown. However there is a problem. Since the variable score (which is used to keep track of the score) is part of an object in my game scene, I can’t acces the score variable in my end_screen scene.

Player Object code:
enter code hereusing UnityEngine;
using UnityEngine.UI;
using System.Collections;

public class PacMan_Controller : MonoBehaviour {

	public float speed;
	public float gravity = 20.0f;
	public bool play = false;
	public int score;
	private Vector3 moveDirection = Vector3.zero;
	private int count;
	private int totalPickupCount;
	public Text scoreText;

	// Use this for initialization
	void Start () 
	{
		DontDestroyOnLoad (transform.gameObject);
		count = 0;
		score = 0;
		totalPickupCount = GameObject.FindGameObjectsWithTag ("PickUp").Length;
		GetComponent<MeshRenderer> ().enabled = false;
	}
	
	// Update is called once per frame
	void FixedUpdate () 
	{
		if (play)
		{
			float moveH = Input.GetAxis ("Horizontal");
			float moveV = Input.GetAxis ("Vertical");
			//Vector3 movement = new Vector3 (moveH, 0.0f, moveV);
	
			//rigidbody.AddForce (movement * speed * Time.deltaTime);

			CharacterController controller = GetComponent<CharacterController>();
			if (controller.isGrounded) {
			//transform.Rotate(0, moveH, 0);
				moveDirection = new Vector3(moveH, 0, moveV);
				moveDirection = transform.TransformDirection(moveDirection);
				moveDirection *= speed;
			}

			moveDirection.y -= gravity * Time.deltaTime;
			controller.Move (moveDirection * Time.deltaTime);
		}
	}

	void OnTriggerEnter(Collider other) 
	{
		if (play)
		{
			if (other.gameObject.tag == "PickUp")
			{
				other.gameObject.SetActive(false);
				count = count + 1;
				score = score + 10;
				scoreText.text = "Score: " + score;
				if (count >= totalPickupCount)
				{
					play = false;
					Application.LoadLevel("Score");
			
				}
			}
		}
	}
}

My End_screen code (Which i’m trying to make it work):

using UnityEngine;
using UnityEngine.UI;
using System.Collections;

public class End_Screen : MonoBehaviour {

	public Text endText;

	// Use this for initialization
	void Start () 
	{
		endText.gameObject.SetActive (true);
		int total = GameObject.Find("PacMan").GetComponent<PacMan_Controller>().score;
		endText.text = "Total Score: " + total;
	}
	
	// Update is called once per frame
	void Update () {
	
	}
}

I’ve tried the DontDestroyOnLoad() function, but I prefer not to do this. Also, it doesn’t even work with this function :stuck_out_tongue:

The error message I receive is: “NullReferenceException: Object reference not set to an instance of an object”.

I hope you can help me with this!

2

Hi, in your example all you want is the score from the game? If that’s the case then maybe something like PlayerPrefs (as suggested by @robertbu) could work. However, I would use DontDestroyOnLoad for a manager class or have a static variable to store the score.

In your example, does the gamObject called “PacMan” exist in the hierarchy in the second scene? I think that gameObjects will still be destroyed if their parent is destroyed. To fix this you could set PacMan object’s transform parent to null at the end of the game before changing scenes.

As another alternative:

public class PacMan_Controller : MonoBehaviour
{
    // Global variable accessible from anywhere - only one
    public static int EndScore = 0;
    // Object member variable - each component object has one
    public int Score = 0;

    // Stores the current objects score in the static score
    public void StoreEndScore()
    {
        EndScore = Score;
    }

    // all your code below...
}

In the above example (not tested), the EndScore should be able to be accessed from anywhere using the call PacMan_Controller.EndScore. And, calling StoreEndScore will populate the static saved score (only stored at runtime not persistent), shown below:

PacMan_Controller myPacMan = GameObject.Find("PacMan").GetComponent<PacMan_Controller>();
myPacMan.StoreEndScore();

I hope that helps =)

3

My suggestion would be to make the class singleton.
This will maintain one instance of the class and all variables will persist the values for single session of game .

4

Check out the saving and persistence tutorial.

Choose the method that works for you. In order from simplest to most powerful

  • Static
  • Singleton
  • Playerprefs
  • Sterilization to file
  • Web server (I don’t think the video covers this option)

You probably want a static variable or a singleton. The others are probably overkill.