Traveler

The Traveler class allows you to easily load and unload scenes (additively or not) and provides UniTasks to manage your call orders in code. It also handles initial logic in scenes.

Scene Handler

Imagine you need some initial preparations in a scene before everything starts working. To do this, you can define your own SceneHandler for the scene.

public class GameSceneHandler : SceneHandler<GameSceneArgs>
{
    protected override void SetupScene(GameSceneArgs args)
    {
        // Initialization logic here
    }
}

public class GameSceneArgs : SceneArgs
{
    // Define additional data here
}

What is the GameSceneArgs Class?

The GameSceneArgs class allows you to provide additional data to the scene when loading it. For example, you might need to create several levels with different difficulties. Instead of creating a separate scene for each difficulty, you can set up one scene and change its logic based on the data provided to it.

Here's an example:

public class PingPongSceneHandler : SceneHandler<PingPongSceneArgs>
{
    [SerializeField] private Enemy m_Enemy;

    protected override void SetupScene(PingPongSceneArgs args)
    {
        m_Enemy.SetSpeed(args.EnemySpeed);
    }
}

[Serializable]
public class PingPongSceneArgs : SceneArgs
{
    public float EnemySpeed;
}

In this example, we set the enemy's speed defined by PingPongSceneArgs. The SceneArgs class is derived from ScriptableObject, so you can create multiple PingPongSceneArgs assets for each difficulty and bind them to difficulty buttons in your menu scene.

You can also override the OnUnloadCallback method to perform some logic before the scene unloads.

Scene Loading

To load a scene, simply call:

Traveler.LoadScene("MySceneName", new MySceneArgs { data = "Hello World!" });

This method returns a UniTask, so you can await it to manage your calls if needed:

await Fader.In(0.2f);
await Traveler.LoadScene("MySceneName");
await Fader.Out(0.2f);

Scene Unloading

To unload a scene, simply call:

Traveler.UnloadScene("MySceneName");

You can also unload all scenes except MAIN by calling:

Traveler.UnloadAllScenes();

These methods also return a UniTask.

The LoadScene method has an overload that allows you to get the SceneHandler. If you know the type of SceneHandler for the scene you are loading, you can use this type as a generic:

var handler = await Traveler.LoadScene<PingPongSceneHandler>();

If you want to get the SceneHandler after opening a scene, you can still do that using the following syntax:

var handler = Traveler.TryGetSceneHandler<PingPongSceneHandler>();

or

var handlers = Traveler.TryGetAllSceneHandlers<PingPongSceneHandler>();

if you have multiple scenes with this type of handler.

Loading Order

After calling the LoadScene method of the Traveler class, it will wait for the current operations (loading/unloading scenes) to finish. Then the scene will be loaded as usual, and a SceneLoadingMessage will be fired. After the scene finishes loading, a SceneLoadedMessage fires, and all objects in the scene will be traversed. If any object contains a SceneHandler, it will be initialized by the Updater and will start preparing the scene. Then all objects in the scene will be initialized, and a SceneOpenedMessage will fire.

IMPORTANT! The scene handler must be a root game object in the scene.

On the UnloadScene call, it will wait until the current operations (loading/unloading scenes) are done. Then a SceneUnloadingMessage fires. If a SceneHandler exists on this scene, the OnSceneUnload method will be invoked, and all objects in the scene will be removed from the Updater processing. Finally, it unloads the scene as usual, waits for it to finish, and fires a SceneUnloadedMessage.