singleton.cs

using UnityEngine;

public class Singleton<T> : MonoBehaviour where T : Singleton<T>
{
	protected static T instance;
 
	/**
	   Returns the instance of this singleton.
	*/
	public static T Instance
	{
		get
		{
			if (instance != null) return instance;
			
			instance = (T) FindObjectOfType(typeof(T));
 
			if (instance == null)
			{
				Debug.LogError(string.Format("An instance of {0} is needed in the scene, but there is none.", typeof(T)));
			}

			return instance;
		}
	}

	public static bool IsInitialized
	{
		get { return instance != null; }
	}

	protected virtual void OnDestroy()
	{
		if (instance == this)
		{
			instance = null;
		}
	}
}