Singleton template for MonoBehaviour class in Unity3D

Singleton.cs

//#define LOG_MESSAGES

using UnityEngine;

public class Singleton<T> : MonoBehaviour where T : MonoBehaviour
{
    private static T _instance;

    /**
       Returns the instance of this singleton.
    */
    public static T Instance 
    {
        get
        {
            if (_instance == null)
            {
                _instance = (T)FindObjectOfType(typeof(T));

                if (_instance == null)
                {
                    #if LOG_MESSAGES
                    Debug.LogError("An instance of " + typeof(T) + "is needed in the scene, but there is none.");
                    #endif
                }
            }
            return _instance;
        }
    }
}