How to pass data (and references) between scenes in Unity

Question

How can I pass score value from one scene to another?

I've tried the following:

Scene one:

void Start () {     score = 0;     updateScoreView ();     StartCoroutine (DelayLoadlevel(20)); }  public void updateScoreView(){     score_text.text = "The Score: "+ score; }  public void AddNewScore(int NewscoreValue){     score = score + NewscoreValue;     updateScoreView (); }  IEnumerator DelayLoadlevel(float seconds){             yield return new WaitForSeconds(10);     secondsLeft = seconds;     loadingStart = true;     do {                 yield return new WaitForSeconds(1);     } while(--secondsLeft >0);      // here I should store my last score before move to level two     PlayerPrefs.SetInt ("player_score", score);     Application.LoadLevel (2); } 

Scene two:

public Text score_text; private int old_score;  // Use this for initialization void Start () {         old_score = PlayerPrefs.GetInt ("player_score");     score_text.text = "new score" + old_score.ToString ();       } 

but nothing displayed on screen, and there's no error.

Is this the correct way to pass data ?

I am using Unity 5 free edition, develop game for Gear VR (meaning the game will run in android devices).

Any suggestion?

Answer 1

There are many ways to do this but the solution to this depends on the type of data you want to pass between scenes. Components/Scripts and GameObjects are destroyed when new scene is loaded and even when marked as static.

In this answer you can find

• 1. Use the static keyword
• 2. Use DontDestroyOnLoad
• 3. Store the data local
  • 3a PlayerPrefs
  • 3b serialize to XML/JSON/Binary and use FileIO

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1. Use the static keyword.

Use this method if the variable to pass to the next scene is not a component, does not inherit from MonoBehaviour and is not a GameObject then make the variable to be static.

Built-in primitive data types such as int, bool, string, float, double. All those variables can be made a static variable.

Example of built-in primitive data types that can be marked as static:

static int counter = 0; static bool enableAudio = 0; static float timer = 100; 

These should work without problems.

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Example of Objects that can be marked as static:

public class MyTestScriptNoMonoBehaviour {  } 

then

static MyTestScriptNoMonoBehaviour testScriptNoMono;  void Start() {     testScriptNoMono = new MyTestScriptNoMonoBehaviour(); } 

Notice that the class does not inherit from MonoBehaviour. This should work.

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Example of Objects that cannot be marked as static:

Anything that inherits from Object, Component or GameObject will not work.

1A.Anything that inherits from MonoBehaviour

public class MyTestScript : MonoBehaviour  {  } 

then

static MyTestScript testScript;  void Start() {     testScript = gameObject.AddComponent<MyTestScript>(); }  

This will not work because it inherits from MonoBehaviour.

1B.All GameObject:

static GameObject obj;  void Start() {     obj = new GameObject("My Object"); }   

This will not work either because it is a GameObject and GameObject inherit from an Object.

Unity will always destroy its Object even if they are declared with the static keyword.

See #2 for a workaround.

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2.Use the DontDestroyOnLoad function.

You only need to use this if the data to keep or pass to the next scene inherits from Object, Component or is a GameObject. This solves the problem described in 1A and 1B.

You can use it to make this GameObject not to destroy when scene unloads:

void Awake()  {     DontDestroyOnLoad(transform.gameObject); } 

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You can even use it with the static keyword solve problem from 1A and 1B:

public class MyTestScript : MonoBehaviour  {  } 

then

static MyTestScript testScript;  void Awake()  {     DontDestroyOnLoad(transform.gameObject); }  void Start() {     testScript = gameObject.AddComponent<MyTestScript>(); }  

The testScript variable will now be preserved when new scene loads.

3.Save to local storage then load during next scene.

This method should be used when this is a game data that must be preserved when the game is closed and reopened. Example of this is the player high-score, the game settings such as music volume, objects locations, joystick profile data and so on.

Thare are two ways to save this:

3A.Use the PlayerPrefs API.

Use if you have just few variables to save. Let's say player score:

int playerScore = 80; 

And we want to save playerScore:

Save the score in the OnDisable function

void OnDisable() {     PlayerPrefs.SetInt("score", playerScore); } 

Load it in the OnEnable function

void OnEnable() {     playerScore  =  PlayerPrefs.GetInt("score"); } 

3B.Serialize the data to json, xml or binaray form then save using one of the C# file API such as File.WriteAllBytes and File.ReadAllBytes to save and load files.

Use this method if there are many variables to save.

General, you need to create a class that does not inherit from MonoBehaviour. This class you should use to hold your game data so that in can be easily serialized or de-serialized.

Example of data to save:

[Serializable] public class PlayerInfo {     public List<int> ID = new List<int>();     public List<int> Amounts = new List<int>();     public int life = 0;     public float highScore = 0; } 

Grab the DataSaver class which is a wrapper over File.WriteAllBytes and File.ReadAllBytes that makes saving data easier from this post.

Create new instance:

PlayerInfo saveData = new PlayerInfo(); saveData.life = 99; saveData.highScore = 40; 

Save data from PlayerInfo to a file named "players":

DataSaver.saveData(saveData, "players"); 

Load data from a file named "players":

PlayerInfo loadedData = DataSaver.loadData<PlayerInfo>("players");