DoNotDestroyOnLoad --- How can I prevent duplicay !!!!

Unity Engine
1

Hi,
DoNotDestroyOnLoad used to keep the GO for next level, that’s good and work well no problem at all. But I’m facing problem like this:

I have a GO named “game_controller” and in this GO has an JS scripted component where I defined it in the Awake function as DoNotDestroyOnLoad(). So, this GO is not destroying across the game. I defined it in the Main_Menu scene. So, when I’m entering in to game and come back to Main Menu again by Application.LoadLevel(“Main_Menu”) then I’m getting another instance of “game_controller” and this is Unity should do. My question is, how can I prevent it?

I have an solution like making this GO into another scene like splash which will never get call. But is there any better idea rather than this?

Thanks.

2

This is not really iPhone related - more related to scripting in general. What I use for this kind of thing is something like the following code (this is C# but should be easy to convert to UnityScript in case you need that):

    #region Unity Singleton Pattern
    private static <YourClassName> instance = null;
    /// <summary>
    ///     Gets the singleton instance of the <YourClassName>.
    /// </summary>
    public static <YourClassName> Instance {
        get { return instance; }
    }

    /// <summary>
    ///     Initializes the <YourClassName> 
    ///     singleton instance or destroys 
    ///     obsolete instances.
    /// </summary>
    void Awake() {
        if (instance != null  instance != this) {
            Destroy(this.gameObject);
            return;
        } else {
            instance = this;
        }

        DontDestroyOnLoad(this.gameObject);
    }
    #endregion Unity Singleton Pattern

IIRC, this is from Workflow and Asset Pipeline (I may have modified it somewhat to suit my needs, but I think it’s actually exactly the way it was introduced there).

3

There is also a set of singleton scripts on the wiki that might be of help. Your idea of loading in a one-time-only splash screen would also work.

FYI, I’m moving this to “scripting” since it isn’t iPhone specific.

4

Thanks Guys! I was also thinking about GetInstanceId() like the singleton C# scripting. May be this should work.

But I wish if Unity support built in Singleton; this will be nice. So, I should give post in WISH LIST. :smile:

BTW, thanks for your help.

5

Are you serious?

UML tools might include Singletons or other patterns but I really don’t see what use would be including “out-of-the-box” design patterns in a game engine (in the sense that Unity would “have” singletons). Okay - when dealing with game objects you can’t use “the pure Singleton pattern”, but it’s “close enough” :wink: