Unity Singleton Helper Classes

Singleton.cs

/// <summary>
/// Singleton class
/// </summary>
public class Singleton<T> where T : new()
{
	/// <summary>
	/// Holds the actual instance
	/// </summary>
	private static T _instance;

	/// <summary>
	/// Accessor for the instance of the singleton
	/// </summary>
	public static T Instance {
		get {
			// Create a new instance if needed
			if (null == _instance)
			{
				_instance = new T();
			}

			return _instance;
		}
	}

	/// <summary>
	/// Protected constructor to prohibit external creation
	/// </summary>
	protected Singleton() { }
}

SingletonBehaviour.cs

using UnityEngine;

/// <summary>
/// Singleton behavior class
/// </summary>
public class SingletonBehaviour<T> : MonoBehaviour where T : Component
{
	/// <summary>
	/// Holds the actual instance
	/// </summary>
	private static T _instance;

	/// <summary>
	/// Accessor for the instance of the singleton
	/// </summary>
	public static T Instance {
		get {
			// Attempt to find an existing instance if necessary
			if (null == _instance)
			{
				_instance = FindObjectOfType(typeof(T)) as T;
			}

			// If the instance is still null, create a new one
			if (null == _instance)
			{
				var go = new GameObject();
				// Hide the object so this script can manage it directly
				go.hideFlags = HideFlags.HideAndDontSave;
				_instance = go.AddComponent<T>();
			}

			return _instance;
		}
	}

	/// <summary>
	/// Constructor that deletes the object if an instance already exists
	/// </summary>
	public SingletonBehaviour()
	{
		if (null != _instance)
		{
			Destroy(this);
		}
	}
}