Using DontDestroyOnLoad for Data Passing Between Scenes in Unity

In Unity game development, when a scene is loaded, all objects in the current scene are destroyed by default, leading to the loss of component, script, and game object data. To pass data such as scores or player states between scenes, developers must employ specific techniques. This article elaborates on the DontDestroyOnLoad method based on best practices and supplements it with other viable approaches to ensure data persistence and accessibility.

Using the DontDestroyOnLoad Method

DontDestroyOnLoad is a function in the Unity API that allows specified game objects to persist across scene transitions. This is particularly useful for MonoBehaviour scripts or game objects that need to be shared between scenes. From the provided QA data, Answer 3 emphasizes the simplicity of this method, especially for preserving variables attached to scripts.

The implementation involves calling DontDestroyOnLoad in the Awake or Start method of a script. For example, if a script is responsible for storing scores, it can be attached to an empty game object and marked as non-destroyable:

using UnityEngine;

public class ScoreManager : MonoBehaviour
{
    public int score = 0;

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

In this example, the ScoreManager script persists when loading new scenes, enabling the retention of the score variable. Developers can access the data in other scenes by finding or referencing this object. Note that this method is suitable for Unity Objects, Components, or GameObjects but may require static references for enhanced accessibility.

Other Methods for Data Passing Between Scenes

Beyond DontDestroyOnLoad, Answer 1 and Answer 2 provide supplementary approaches, as outlined below:

• Static Variables: For non-Unity objects (e.g., primitive data types or custom classes), the static keyword can be used. For instance, static int playerScore = 100;. However, Unity Objects such as MonoBehaviours are destroyed on scene load even if marked static, so this is not recommended for complex objects.
• ScriptableObject: As a data container, ScriptableObjects persist in the Assets and can be used for data sharing during a session. Answer 2 demonstrates how to create and reference ScriptableObject instances, but serialization is needed for permanent data storage.
• Local Storage: Use PlayerPrefs or file I/O (e.g., JSON serialization) to save data to the device. This preserves data after the game is closed, making it ideal for scores, settings, etc. For example, store data with PlayerPrefs.SetInt("score", score); and retrieve it in a new scene with PlayerPrefs.GetInt("score");.

In summary, DontDestroyOnLoad is suitable for temporary data passing, while static variables and local storage are better for permanent data. Developers should choose methods based on data type, persistence requirements, and performance considerations.