유니티 Singleton 싱글톤 노트

    private static GameManager instance = null;

    private void Awake()
    {
        if (null == instance) {
            instance = this;
            DontDestroyOnLoad(this.gameObject);
        }
        else 
        {
            Destroy(this.gameObject);
        }
    }
    public static GameManager Instance 
    {
        get 
        {
            if (null == instance)
            {
                return null;
            }
            return instance;
        }
    }