RuntimeInitializeOnLoadMethod only on certain scenes

Question

I'm using [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.BeforeSceneLoad)] to initialize a prefab that contains all the components required for the game to work propertly.

public class FrameworkInitializer : MonoBehaviour
{
    [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.BeforeSceneLoad)]
    public static void InitializeFramework()
    {
       Instantiate(Resources.Load("_GameEngine")) as GameObject;
    }
}

It works fine.

Now I'm creating some scenes to try out things before implementing them in the final game, and I don't really need the default prefab to initialize. I tried adapting the script to this:

public class FrameworkInitializer : MonoBehaviour
{
    [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.BeforeSceneLoad)]
    public static void InitializeFramework()
    {
        if (GameObject.FindWithTag("Framework Support") != null) return;
        if (GameObject.Find("NoFrameworkSupportRequired") != null)
        {
            Debug.LogWarning("Carla Framework initializer skipped because of NoFrameworkSupportRequired gameobject in scene.");
            return;
        }
        var framework = Instantiate(Resources.Load("_GameEngine")) as GameObject;
    }
}

But it's not working, because the scene is not loaded yet so it can't find any gameobject.

And if I change BeforeSceneLoad to AfterSceneLoad, some of the scripts that require the prefab in the Awake and onEnable cycle fails.

How can I make this script to run only on some of the scenes?

Answer 1

I think you might want to make your _GameEngine/framework the singleton.

public class Framework : MonoBehaviour {
    static Framework _instance;
    public static Framework Instance {
        get {
            if (_instance == null) {
                _instance = Instantiate(Resources.Load<Framework>("_GameEngine"));                    
            }
            return _instance;
        }
    }

    // On the _GameEngine prefab, assign references to each of the child components
    // that other scripts might want to look up.
    public DialogueSystemManager dialogue;
    public OtherManager other;
    // etc.
}

Now this behaves as a service locator. Anything else in your scene that wants to access a singleton manager does so via the Framework. ie..

DialogueSystemManager.Instance

becomes

Framework.Instance.dialogue

Now anytime anything references a manager contained in the Framework, it does so via the Framework singleton's lazy instantiation, ensuring it exists "just in time", but only when needed, so it won't get spawned in scenes where no one asks for it.

Answer 2

I had the same question when setting up some test scenes that I did not want to use my manager GameObject. I am using a similar method, also setting DontDestroyOnLoad after instantiation.

I ended up checking the scene name beforehand. The method using RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.BeforeSceneLoad) does appear to know the name of the scene, even though it has not loaded yet.

Include in your namespaces:

using UnityEngine.SceneManagement;  

And then do whatever check you want to do in the function before the instantiation. In my case, I am excluding any Scene that starts with "Test", along with the default scene name created by Unit Tests (e.g. "InitTestScene637801810867719397"):

Scene scene = SceneManager.GetActiveScene();
if (!scene.name.StartsWith("Test") && !scene.name.StartsWith("InitTestScene"))