Singleton System

A lightweight Unity package for runtime singletons and attribute-driven auto singleton generation.

Requirements

• Unity 2022.3 or newer

Runtime MonoSingleton

Create a singleton component by inheriting from MonoSingleton<T>.

using Sinsam.SingletonSystem;

[AutoSingleton]
public sealed class GameManager : MonoSingleton<GameManager>
{
    protected override void InitializeSingleton()
    {
        // Initialize once here.
    }
}

Access it with:

GameManager.Instance;

Instance automatically creates the singleton when it is missing, unless the singleton is blocked by a scene rule.

AutoSingleton generation

Add [AutoSingleton] to a concrete MonoSingleton<T> class.

[AutoSingleton(loadOnStart: true, createPrefab: true)]
public sealed class AudioManager : MonoSingleton<AudioManager>
{
}

The editor generator scans attributed singleton types, creates prefabs under:

Assets/Resources/AutoSingletons

and writes the startup registry to:

Assets/Resources/SingletonRegistry.asset

The generator runs after script reload and can also be run manually from:

Tools > Singleton System > Generate Auto Singleton Registry

Attribute options

• loadOnStart: if true, the generated or discovered prefab is added to SingletonRegistry and automatically instantiated when allowed by the current scene rules.
• createPrefab: if true, the editor creates or updates a prefab automatically. If false, the generator searches for an existing prefab under Assets/Resources/AutoSingletons.

Scene scoped singletons

SingletonRegistry can restrict a singleton to specific scenes. This is useful for managers such as BattleManager, StageManager, or DungeonManager that should exist only inside a gameplay context.

Open:

Assets/Resources/SingletonRegistry.asset

Then add an entry to Scene Rules:

Prefab: BattleManager
Allow All Scenes: false
Destroy When Scene Not Allowed: true
Scene Names:
  - BattleScene
  - BossBattleScene

With that setup:

• BattleManager is created only when the active or loaded scene is BattleScene or BossBattleScene.
• BattleManager.Instance returns null and logs a warning outside registered scenes.
• If a persistent BattleManager exists and the active scene changes to an unregistered scene, BattleManager.DestroyInstance() is called automatically.
• If a BattleManager object is placed directly in an unregistered scene, it is destroyed during Awake().

Scene names can be either scene.name, such as BattleScene, or scene.path, such as Assets/Scenes/BattleScene.unity.

Rules are optional. If a singleton has no scene rule, it keeps the previous global behavior and can be created in any scene.

Plain C# Singleton

For non-MonoBehaviour classes:

using Sinsam.SingletonSystem;

public sealed class SaveService : Singleton<SaveService>
{
    public SaveService()
    {
    }
}

Access it with:

SaveService.Instance;