Objective-C: int value changing without cause

Question

Objective-C: I need help retaining the value of an int. It's changing on me without my command.

The original question was: "How do you declare and retain an int?", that was satisfied in another post here: http://stackoverflow.com/questions/1938513

Now I have a problem where an int that was 18 is changing to 2, somehow on its own.

Here's my code:

@interface Game : Layer // this is from cocos2d
{
   int maxSprites;
}

@implementation Game
-(void)initVariables
{
  maxSprites = 18;
}

Later on, when I print it out, like

 NSLog(@" maxSprites = %d  ", maxSprites);

I get:

 maxSprites = 2

And operations that require it to be 18, crash or don't work, as if it's really just 2 now.

How would that be possible? =)

Apple + Shift + F reveals no other usage of the maxSprites variable.

I've looked at other code examples and often they're exposing the variable with a getter and setter, and they are also using @property. Am I missing something? I'm new to Objective-C, so I might as well just be!

I did a Apple + Shift + F for maxSprites" In Project, Textual, Contains, Ignore Case and only resulted in:

       Game.h:  int maxSprites;
       Game.m:  maxSprites = 18;
       Game.m:  NSLog(@" maxSprites  = %d", maxSprites);
       Game.m:  NSLog(@" maxSprites  = %d", maxSprites);
       Game.m:  NSLog(@"maxSprites is at %p", &maxSprites);
       Game.m:  NSLog(@"maxSprites is at %p", &maxSprites);
       Game.m:  NSLog(@" maxSprites  = %d", maxSprites);
       Game.m:  NSLog(@" maxSprites  = %d", maxSprites);
       Game.m:  NSLog(@"maxSprites is at %p", &maxSprites);
       Game.m:  NSLog(@"maxSprites is at %p", &maxSprites);

I found the location where it changes using a watchpoint. It changes

    Expression: “*(int *) 67379960”
    New Value: 2
    Old  Value: 18

on this line:

   [self checkMatchBarAward:spriteTypeToAdd];

Odd? That function doesn't do anything with maxSprites, nor does that line.

EDIT: here is the function, I commented everything inside it out and it still occurs: .h

    -(void)checkMatchBarAward:(int)spriteTypeToAdd;

.m

     -(void)checkMatchBarAward:(int)spriteTypeToAdd
      {
      }

EDIT:

Thanks for the recommendations. I have cleaned all targets and it still changed values. Because of the answers you guys/gals gave, you lead me to the problem. Thanks for all of your help.

I posted my results below in an answer. Here's a copy:

Guys/gals you wouldn't believe what was the cause. Thank you for all your help because telling me to clean and look and check my types, that helped.

I looked over my arrays. I found one that was declared like this:

  int matchBarArray[8];

2 lines up from the breakpoint halt where it says that the value changed from 18 to 2, I have this line:

  matchBarArray[spritesCaptured-1] = spriteTypeToAdd;

And guess what, I overstepped the bounds of the array by 1. If I increase the size of the array to 9, I no longer get the int change from 18 to 2.

Also, if I overstep the bounds by more than 1, that is, I reduce the array size to smaller, there are other things that start changing such as my score, booleans, the whole game ! =)

I can't believe hitting memory outside the array in Objective-C can cause such a riot =) AND IT'S SO HARD TO DEBUG!

Answer 1

I didn't see the line you specify in your code.

Chances are, though, that you are referring to something as a long* when it's an int* or something like that (although how, after all these years, C STILL can't see that is beyond me).

Anyway, check your types where the sizes of what they point to may differ. If you reference an int * memory location with a long * (say, by passing in an int* to a method that expects a long*), you will fubar the stack and start modifying adjacent variables.

I've done this more than once, but in C, not Objective C--so I'm not sure it's the correct answer.

Answer 2

If your checkMatchBarAward: method truly is empty, then you need to clean your project (Shift + cmd + k) and rebuild it.

Answer 3

Guys/gals, you wouldn't believe what was the cause. Thank you for all your help because telling me to clean and look and check my types, that helped.

I looked over my arrays. I found one that was declared like this:

  int matchBarArray[8];

2 lines up from the breakpoint halt where it says that the value changed from 18 to 2, I have this line:

  matchBarArray[spritesCaptured-1] = spriteTypeToAdd;

And guess what, I overstepped the bounds of the array by 1. If I increase the size of the array to 9, I no longer get the int change from 18 to 2.

Also, if I overstep the bounds by more than 1, that is, I reduce the array size to smaller, there are other things that start changing such as my score, booleans, the whole game ! =)

I can't believe hitting memory outside the array in Objective-C can cause such a riot =) AND IT'S SO HARD TO DEBUG!