Hi,

I'm a beginner level programmer trying to make a game app for the iphone and I've encountered a possible issue with the memory management (exc_bad_access) of my program so far. I've searched and read dozens of articles regarding memory management (including apple's docs) but I still can't figure out what exactly is wrong with my codes. So I would really appreciate it if someone can help clear up the mess I made for myself.

//in the .h file
@property(nonatomic,retain) NSMutableArray *fencePoleArray;
@property(nonatomic,retain) NSMutableArray *fencePoleImageArray;
@property(nonatomic,retain) NSMutableArray *fenceImageArray;

//in the .m file
- (void)viewDidLoad {
    [super viewDidLoad];
    self.gameState = gameStatePaused;

    fencePoleArray = [[NSMutableArray alloc] init];
    fencePoleImageArray = [[NSMutableArray alloc] init];
    fenceImageArray = [[NSMutableArray alloc] init];

    mainField = CGRectMake(10, 35, 310, 340);

    ..........

    [NSTimer scheduledTimerWithTimeInterval:0.05 target:self selector:@selector(gameLoop) userInfo:nil repeats:YES];
}

So basically, the player touches the screen to set up the fences/poles

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    if(.......) {

    .......

    }
    else {
        UITouch *touch = [[event allTouches] anyObject];
        currentTapLoc = [touch locationInView:touch.view];

        NSLog(@"%i, %i", (int)currentTapLoc.x, (int)currentTapLoc.y);

        if(CGRectContainsPoint(mainField, currentTapLoc)) {
            if([self checkFence]) {
                onFencePole++;
                //this 3 set functions adds their respective objects into the 3 NSMutableArrays using addObject:
                [self setFencePole];
                [self setFenceImage];
                [self setFencePoleImage];

                .......

                }
            }
            else {
                .......
            }
        }
    }
}

The setFence function (setFenceImage and setFencePoleImage is similar to this)

-(void)setFencePole {
    Fence *fencePole;
    if (!elecFence) {
        fencePole = [[Fence alloc] initFence:onFencePole fenceType:1 fencePos:currentTapLoc];
    }
    else {
        fencePole = [[Fence alloc] initFence:onFencePole fenceType:2 fencePos:currentTapLoc];
    }
    [fencePoleArray addObject:fencePole];
    [fencePole release];

and whenever I press a button in the game, endOpenState is called to clear away all the extra images(fence/poles) on the screen and also to remove all existing objects in the 3 NSMutableArray. Point is to remove all the objects in the NSMutableArrays but keep the array itself so it can be reused later.

-(void)endOpenState {

    ........

    int xMax = [fencePoleArray count];
    int yMax = [fenceImageArray count];

    for (int x = 0; x < xMax; x++) {
        [[fencePoleImageArray objectAtIndex:x] removeFromSuperview];
    }

    for (int y = 0; y < yMax; y++) {
        [[fenceImageArray objectAtIndex:y] removeFromSuperview];
    }

    [fencePoleArray removeAllObjects];
    [fencePoleImageArray removeAllObjects];
    [fenceImageArray removeAllObjects];

    ........
}

The crash happens here at the checkFence function.

-(BOOL)checkFence {
    if (onFencePole == 0) {
        return YES;
    }
    else if (onFencePole >= 1 && onFencePole < currentMaxFencePole - 1) {
        CGPoint tempPoint1 = currentTapLoc;
        CGPoint tempPoint2 = [[fencePoleArray objectAtIndex:onFencePole-1] returnPos]; // the crash happens at this line
        if ([self checkDistance:tempPoint1 point2:tempPoint2]) {
            return YES;
        }
        else {
            return NO;
        }
    }
    else if (onFencePole == currentMaxFencePole - 1) {

    ......

    }
    else {
        return NO;
    }
}

So the problem here is, everything works fine until checkFence is called the 2nd time after endOpenState is called. So its like tap_screen -> tap_screen -> press_button_to_call_endOpenState -> tap screen -> tap_screen -> crash

What I'm thinking of is that fencePoleArray got messed up when I used [fencePoleArray removeAllObjects] because it doesn't crash when I comment it out. It would really be great if someone can explain to me what went wrong. And thanks in advance.