cocos2d for iPhone

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1. 

   eshirt
   Member

   Maybe it's something completely obvious, but I'm having trouble figuring out the most efficient way to store game data like "player selected", "current position", etc. I'm not talking about global settings (sound on/off, etc), those would be stored in a .plist, but when a player starts a new game, there are certain variables that I want to persist.

   The way I was trying to accomplish this was to create a class called GameData, where I set properties for all the variables. Then I was planning on calling something like myGame = [GameData newGame] and setting/getting variables using myGame.myCharacter and the like.

   I can't seem to get this to work on several levels, but mainly I can't seem to get the object myGame to persist between Layers within the same Scene. Am I approaching this incorrectly? What are some best practices for storing this kind of persistent game data? Does my question even make sense? :)

   Posted 2 years ago #
2. 

   jd
   Member

   Use the search. This has been discussed and I remember one thread that had lots of great information that will give you a great start if not everything you need.

   Posted 2 years ago #
3. 

   pabloruiz55
   Member

   it was this one, i think:
   http://www.cocos2d-iphone.org/forum/topic/737#post-8224

   Posted 2 years ago #
4. 

   Kahless
   Member

   This site has some nice code for a singleton.

   http://cocoawithlove.com/2008/11/singletons-appdelegates-and-top-level.html

   Posted 2 years ago #
5. 

   eshirt
   Member

   Thanks for the links! Sorry - I hate duplicating questions, but I must have missed that thread in my search. I'll take a look at what Clain wrote and the post.

   Any other thoughts on singletons that aren't covered in the thread already, I'd be glad to hear them. Is my approach to saving game state considered "wrong" in OOP?

   Posted 2 years ago #
6. 

   onedayitwillmake
   Member

   Hey, i also as a person who's new to this wrote up something about this just yesterday. Not trying to spam my own blog, but its exactly what you're looking for and the usage case is prob similar to your own.

   http://www.learningiphone.com/?p=81 - Creating a global object in Objective-C

   Posted 2 years ago #
7. 

   eshirt
   Member

   Thanks, onedayitwillmake - between the three links, I'm starting to get the whole concept.

   Would it make sense to have two singletons, one for GameData, another for GameSettings?

   In my case, there are characters getting selected for each new game, but settings persist across many games. Or should I just try to handle it all in one for sake of neatness?

   Posted 2 years ago #
8. 

   onedayitwillmake
   Member

   Well that's more subjective than anything else, however. I would say the cleanest (prob have to writeout the most code thoug) way would be to have a Global singleton settings object, that contains a Data and a Settings (new better names for those prob exist though since settings are data so it could get confusing) object.

   This way you're still going with the whole Global settings theme, and when you wipe it (should you need to, maybe to restore defaults) - you're wiping one thing and it can contain all your defaults in its -init function. Less to manage in the long run

   Posted 2 years ago #
9. 

   slipster216
   Moderator

   I personally prefer using extern over the singleton pattern when I can. It just makes it less verbose to access the data.

   // using extern
   TheApp.somevariable
   
   // instead of as a singleton
   [MyAppDelegate instance].somevariable

   Posted 2 years ago #
10. 

    eshirt
    Member

    @slipster216, I think I read a bit of conversation about extern either by you or another member in another post. Would you mind elaborating on (or pointing me in the right direction) the setup and implementation of extern variables? Sorry - I'm getting more and more familiar with a lot of the Obj-C language, but is that a C language practice?

    With all your help, I think I understand the concept of using a singleton and its risks/benefits. Would you say that using extern requires prior experience, or is it a trivial concept?

    Sorry to show my ignorance there, but thanks for the help!

    Posted 2 years ago #
11. 

    slipster216
    Moderator

    it's a C thing I believe. Having an extern class pointer isn't much different than a singleton, just a little simpler on the syntax IMO. So:

    // MyClass.h
    
    // blah blah
    
    extern MyClass* TheClass;

    // in the .m before the implementation
    
    MyClass* TheClass = nil; // 
    
    -(id)init
    {
       self = [super init];
       if (self)
       {
          // release the current version if it exists
          if (TheClass)
             [TheClass release];
          TheClass = self;
    
       }
       return self;
    }

    Then you have to actually initialize it somewhere:

    [[MyClass alloc] init];

    And you can now type:

    // from anywhere in your code, in any class
    TheClass.someproperty

    typed from memory, so buyer beware...

    Posted 2 years ago #
12. 

    eshirt
    Member

    Interesting... Makes sense - and I don't see any reason not to use it. Other than syntax, is there a tradeoff using one way or the other?

    Posted 2 years ago #
13. 

    chrisco
    Member

    I'm curious about this too. An Extern class seems pretty clean compared to what I'm doing now - I've been storing this sort of information in my app delegate. Then I call something like:

    uint score = (MyAppDelegate *)[[UIApplication sharedApplication] delegate].score; // just an example...

    Obviously that looks like hell :P

    Posted 2 years ago #
14. 

    slipster216
    Moderator

    None that I know of.

    Posted 2 years ago #
15. 

    leftright
    Member

    I use the NSUserDefaults to save game states and user data, and when the user save or terminates the application, I just user the UIApplication Delegate to save the data to the NSUserDefaults.

    Anyone else uses this method?

    Posted 2 years ago #
16. 

    leftright
    Member

    There's also a really nice screencast explaining the in outs of using creating a singleton class posted by 71squared.

    http://www.71squared.com/2009/05/iphone-game-programming-tutorial-7-singleton-class/

    Posted 2 years ago #
17. 

    Codemattic
    Moderator

    @leftright, me too re: NSUserDefaults, but I also save some stuff with .plists to the user's documents folder.

    Posted 2 years ago #
18. 

    abitofcode
    Moderator

    Chapter 3 of iPhone Games Projects has a nice approach http://www.apress.com/book/view/1430219688 the source is available on the website. Makes more sense with the book though.

    Posted 2 years ago #
19. 

    slipster216
    Moderator

    I prefer NSCoding when saving game data; super easy, especially if you plan on serializing a lot of game state.

    Posted 2 years ago #
20. 

    bradparks
    Member

    @slipster216: Thanks for that "extern" stuff for singletons... It really cleaned up the look of my code!

    and as for the NSCoding stuff, here's a few good links:

    http://cocoaheads.byu.edu/wiki/nscoding

    and this post has a discussion that talks about how clain implemented NSCoding for a game he worked on, Dr Bubbles:

    http://www.cocos2d-iphone.org/forum/topic/737

    Posted 2 years ago #
21. 

    mtran003
    Member

    bradparks,

    Presumably, now that you've had some time to use the "extern" method for singletons and the NSCoding stuff--how has that worked out for you? Any further thoughts?

    I'm about to embark on a similar endeavor myself and want to get an updated feedback on how it has worked for you.

    Regards,
    Manny

    Posted 1 year ago #

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