SingletonBehaviour

Abstract generic MonoBehaviour singleton with a three-step lazy-initialization chain: find in scene → load from Resources → create new GameObject. Supports DontDestroyOnLoad, hierarchy/inspector visibility flags, and auto-saves a prefab asset in the editor when the asset path is configured. Extends ParagonBehaviour.

Definition

Namespace: Paragon Assembly: Paragon.dll

[SingletonSettings]
public abstract class SingletonBehaviour<T> : ParagonBehaviour
    where T : SingletonBehaviour<T>

Inheritance: SerializedMonoBehaviour → ParagonBehaviour → SingletonBehaviour<T>

Remarks

SingletonBehaviour<T> is the most full-featured singleton variant. Its resolution chain on first Instance access:

1. Return cached — If instance is already set, return it.

2. Find in scene — FindFirstObjectByType<T>(). Works when the singleton already exists (e.g., placed in a scene).

3. Load from Resources — Resources.Load<T>(AssetPath) and instantiate the prefab. Requires AssetPath to be set in [SingletonSettings].

4. Create new — Creates a new GameObject with AddComponent<T>(). In the editor, automatically saves the result as a prefab at Assets/Resources/{AssetPath}.prefab.

During Awake(), the singleton:

• Asserts that no duplicate instance exists

• Optionally calls DontDestroyOnLoad() based on the attribute

• Applies hierarchy/inspector hide flags

Quick Lookup

Goal	How
Access the singleton	MyManager.Instance
Define a new singleton	Subclass SingletonBehaviour<T>, add [SingletonSettings]
Persist across scene loads	Set DontDestroyOnLoad = true in [SingletonSettings]
Load from a prefab	Set AssetPath = "MyPrefab" (under Resources/)
Initialize at startup	Set InitializeOnLoad = true in [SingletonSettings]
Hide from hierarchy	Set HideInHierarchy = true in [SingletonSettings]

Properties

Instance

Static accessor for the singleton. Triggers lazy initialization on first access.

public static T Instance { get; }

DebugEnabled

Static debug flag that delegates to the instance's ParagonBehaviour.DebugEnabled.

public new static bool DebugEnabled { get; }

Extension Points

Optional Overrides

Method	Return Type	Called When	Purpose
Awake()	void	Unity Awake	Instance assignment, DontDestroyOnLoad, hide flags. Call base.Awake().
OnDestroy()	void	Unity OnDestroy	Clears the static instance reference. Call base.OnDestroy().

Implementation Requirements

When subclassing SingletonBehaviour<T>, you MUST:

1. Apply [SingletonSettings] to the concrete class (or inherit the base attribute)

2. Use the CRTP pattern: class MyManager : SingletonBehaviour<MyManager>

3. Call base.Awake() if overriding Awake() — it assigns the instance and applies settings

4. Call base.OnDestroy() if overriding OnDestroy() — it clears the static instance

You SHOULD:

• Set AssetPath for singletons that need persistent configuration in the Inspector

• Set DontDestroyOnLoad = true for manager objects that must survive scene transitions

• Set InitializeOnLoad = true for singletons needed before any scene code runs

You SHOULD NOT:

• Create multiple instances of the same singleton type — the Debug.Assert in Awake() will fire

• Access Instance during OnDestroy() of another object — the singleton may already be nullified

Type Parameters

Parameter	Constraint	Description
T	SingletonBehaviour<T>	The concrete subclass type (CRTP pattern)

Common Pitfalls

Duplicate instance assertion If two instances of the same singleton exist in a scene (e.g., from a scene reload without DontDestroyOnLoad), Awake() fires a Debug.Assert. Ensure only one instance exists, or use DontDestroyOnLoad = true.

Missing base.Awake() call If you override Awake() without calling base.Awake(), the instance field is never set, DontDestroyOnLoad is not applied, and Instance will re-trigger the initialization chain on next access (potentially creating a second instance).

AssetPath must be a Resources-relative path The AssetPath is passed to Resources.Load<T>(), so it must be relative to a Resources/ folder. Do not include Assets/Resources/ or the file extension.

Editor auto-creation saves to Assets/Resources/ When no asset exists and AssetPath is set, CreateSingleton() auto-saves a prefab at Assets/Resources/{AssetPath}.prefab. Ensure the directory exists or Unity will log an error.

Examples

Basic Manager

using Paragon;
using UnityEngine;

[SingletonSettings(InitializeOnLoad = true, DontDestroyOnLoad = true, AssetPath = "Game Manager")]
public class GameManager : SingletonBehaviour<GameManager>
{
    [SerializeField] private int startingLives = 3;

    public int Lives { get; set; }

    protected override void Awake()
    {
        base.Awake();
        Lives = startingLives;
    }
}

// Usage
GameManager.Instance.Lives--;

Hidden Background Singleton

[SingletonSettings(InitializeOnLoad = true, DontDestroyOnLoad = true, HideInHierarchy = true, HideInInspector = true)]
public class AudioSystem : SingletonBehaviour<AudioSystem>
{
    public void PlaySound(AudioClip clip)
    {
        // ...
    }
}

See Also

• SingletonScriptableObject<T> — ScriptableObject variant

• SingletonObject<T> — plain C# object variant

• SingletonSettingsAttribute — configuration attribute

• SingletonInitializer — startup bootstrap

• ParagonBehaviour — base class

• Singletons Subsystem — subsystem overview