Need help with a memory management problem in my game model
- by user309030
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.
