Why Does My Unity Game Manager Script Only Run Once?

Troubleshooting Unity Game Manager: Single Execution Issue

Problem Overview

In Unity game development, a persistent game manager across scenes is crucial. However, a common problem is a script executing only once at the start, despite its presence in all scenes.

The Root Cause: Missing Preload Scene

Unity lacks an automatic preload mechanism. Without a dedicated preload scene, your game manager's initialization and essential components won't survive scene transitions.

The Solution: Implementing a Preload Scene

Here's how to fix this:

1. Create a Preload Scene: Add a new scene (e.g., "Preload") and make it scene 0 in your Build Settings.
2. Add a Game Object: In the "Preload" scene, create an empty GameObject named "_app".
3. Enable "Don't Destroy On Load": In the Inspector for "_app", check the "Don't Destroy On Load" box.

Attaching Game Manager Components

All your core game manager functionality (database connections, sound management, score tracking, etc.) should be attached as components to the "_app" GameObject in your preload scene. This guarantees their persistence across all subsequent scenes.

Accessing Game Objects from Other Scripts

Two methods exist for accessing game objects from other scripts:

Method 1: FindObjectOfType

Use this in your script's Awake() method:

Sound sound = Object.FindObjectOfType<Sound>();
Game game = Object.FindObjectOfType<Game>();

Method 2: Static Global Variables (More Efficient)

A more streamlined approach uses static global variables:

public static class GameManager
{
    public static Sound sound;
    public static Game game;

    static GameManager()
    {
        GameObject app = GameObject.Find("_app");

        sound = app.GetComponent<Sound>();
        game = app.GetComponent<Game>();
    }
}

Summary

By creating a preload scene and attaching your game manager components to a persistent GameObject, you ensure consistent execution across all your Unity scenes. Choose the object access method that best suits your coding style.

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