cocos2d for iPhone

A fast, easy to use, free, and community supported 2D game engine

1. 

   kevchang30
   Member

   I have a sprite, for example, a ball.
   The ball runs with a scheduler that maps out the ball's route.

   -(void)update:(ccTime)dt {
   ...
   ...
   self.position = ccp(x,y);
   yP = self.position.y;
   xP = self.position.x;
   }

   In another file, I need to grab these updated coordinates and use them for other sprite actions.

   I have tried to write a method within ball.m that returns yP. But NSLog always returns the value as 0.

   Hence, the question is, how do I access these coordinates from another file?

   Thanks

   Kevin

   Posted 2 years ago #
2. 

   Andrew
   Member

   Could you do a method in your ball layer to return the coordinates and call it from your other file?

   +(CGPoint) getPos {
   return [self position];
   }

   then call the method from the other file with something like

   CGPoint ballPos=[ball getPos];
   xP=ballPos.x;
   yP=ballPos.y;

   You might have to play with that a bit, but it should work.

   Cheers,
   Andrew.

   Posted 2 years ago #
3. 

   kevchang30
   Member

   Thanks for the response.

   I've tried different ways to implement what you have posted above.

   However, I get a lot of errors.

   error: request for member 'position' in something not a structure or union
   warning: incomplete implementation of class 'Ball'

   I have tried to "return ccp(xP, yP) for xP = self.position.x and yP = self.position.y.

   But I get this warning: instance variable 'xP' accessed in class method.

   Why doesn't the class recognize "position" when I have used it in another method within the same file?

   Thanks

   Kevin

   Posted 2 years ago #
4. 

   Codemattic
   Moderator

   Hi kevchang30, make a global gBall that points to your ball sprite. Then access that sprite from anywhere! The gBall could be declared a global, or you could make it a member variable of your app delegate and access it through that. Theres an in-depth discussion on globals here:

   http://www.cocos2d-iphone.org/forum/topic/551

   There is also a link to:

   http://www.drobnik.com/touch/2009/05/the-death-of-global-variables/

   which has a good explanation on how to make a singleton/shared-instance - which you could do to your app delegate, and keep a link to your ball from there.

   hth, Codemattic

   Posted 2 years ago #
5. 

   Andrew
   Member

   Hi Kevin. I struck something similar to that too, but assumed it was just me doing something stupid. I think the errors are to do with Objective C limiting what shared methods can access to protect the class from outside classes (because you're declaring it with a + rather than a -). What Codemattic said will work fine. If you make xP and yP global (declare them outside the class declaration), anything that includes that .h file will have access to them.

   Sorry if I wasted some of your time!

   Cheers,
   Andrew.

   Posted 2 years ago #
6. 

   kevchang30
   Member

   Thanks for all the responses.

   Andrew, no worries man. Stumbling upon this right now is better than stumbling upon it later.

   Back to reading more about globals.

   Kevin

   Posted 2 years ago #
7. 

   natanavra
   Member

   Just random question; if your ball is a random object, and you declare it's position as a part of the object and propertirize it - wouldn't you be able to access the position by importing the ball object in another file, initializing it and accessing the position?

   #import "ball.h"
   
   ball *myBall = [[ball alloc] init];
   NSLog(@"x:%f y:%f", myBall.poisition.x, myBall.poisition.y);

   ???

   Posted 2 years ago #
8. 

   pabloruiz55
   Member

   @natanavra: No, in your example you are allocating a different object than the one you had.

   What you would need to do is to pass a reference of the created object or you could pass a reference of the gamelayer and get any object it contains.

   Posted 2 years ago #

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