Memory management with GCD, NSMutableArray and UITableView [closed] - objective-c

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Closed 9 years ago.
I'm now been stuck with this error "EXC_BAD_ACCESS" for hours and I can't seem to find what's wrong. Hopefully some of you will find it.
I'm downloadning a file containing json-data, save it as a custom NSObject in an NSMutableArray and then present it in a UITableView. It's when I going to present it in the UITableView I encounter problems.
ViewController.h
#property (nonatomic, retain) NSMutableArray *menuItems;
ViewController.m
- (void)viewDidLoad
{
[super viewDidLoad];
menuItems = [[NSMutableArray alloc] init];
}
- (void)viewDidAppear:(BOOL)animated
{
[self downloadMenu];
}
-(void)downloadMenu
{
dispatch_queue_t fetchfromServerQueue = dispatch_queue_create("fetchfromServer", NULL);
[self createProgressionAlertWithMessage:#"Fetching menu"];
dispatch_async(fetchfromServerQueue, ^{
NSURL *menuURL = [NSURL URLWithString:#"anURL"];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:menuURL];
NSError *error = nil;
NSURLResponse *response;
NSData *responseData = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
responseArray = [NSJSONSerialization JSONObjectWithData:responseData options:kNilOptions error:&error];
menuItems = [[NSMutableArray alloc] initWithCapacity:[responseArray count]];
for (int i = 0; i<[responseArray count]; i++) {
NSDictionary *menuObject = [responseArray objectAtIndex:i];
NSString *x = [NSString stringWithFormat:#"%#", [menuObject objectForKey:#"x"]];
NSString *y = [NSString stringWithFormat:#"%#", [menuObject objectForKey:#"y"]];
NSString *z = [NSString stringWithFormat:#"%#", [menuObject objectForKey:#"z"]];
MenuItem *menuItem = [[MenuItem alloc] initWithX:x andY:y andZ:z];
[menuItems addObject:menuItem];
[menuItem release];
}
dispatch_async(dispatch_get_main_queue(), ^{
[progressAlert dismissWithClickedButtonIndex:0 animated:YES];
[menuTable reloadData];
});
});
dispatch_release(fetchfromServerQueue);
}
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return [menuItems count];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
MenuItem *menuItem = (MenuItem *)[menuItems objectAtIndex:indexPath.row];
cell.textLabel.text = [NSString stringWithFormat:#"%#", [menuItem x]];
return cell;
}
On "cell.textLabel.text = [NSString stringWithFormat:#"%#", [menuItem x]];" I get "EXC_BAD_ACCESS (code=1,address=0xXXXXXXXX)".
I don't use ARC and can't convert to it in a near future with this project. That make it a problem due to my lack of knowledge with memory management.
Any idea of what's wrong?
Thx!
#### #### #### #### #### #### #### #### ####
This is how MenuItem looks like:
#import <Foundation/Foundation.h>
#interface MenuItem : NSObject
{
NSString *x;
NSString *y;
NSString *z;
}
-(id)initWithX:(NSString *)x_ andY:(NSString *)y_ andZ:(NSString *)z_;
-(NSString *)x;
-(NSString *)y;
-(NSString *)z;
#property(retain, nonatomic) NSString *x;
#property(retain, nonatomic) NSString *y;
#property(retain, nonatomic) NSString *z;
#end
#import "MenuItem.h"
#implementation MenuItem
#synthesize x;
#synthesize y;
#synthesize z;
-(id)initWithX:(NSString *)x_ andY:(NSString *)y_ andZ:(NSString *)z_
{
self = [super init];
if(self)
{
x = x_;
y = y_;
z = z_;
}
return self;
}
-(void)dealloc
{
[x release];
[y release];
[z release];
[super dealloc];
}
-(NSString *)x
{
return x;
}
-(NSString *)y
{
return y;
}
-(NSString *)z
{
return z;
}
#end

Answer 1

I don't see anything obvious, perhaps something in menuItem is causing the issue? What does [menuItem x] do?
In general, run the app with the zombies instrument: cmd-i, then select Zombies. This will give you a trace of the allocations/releases of the object which is throwing the EXC_BAD_ACCESS.
Good luck.

Answer 2

This is a bit weird:
-(void)downloadMenu
{
dispatch_queue_t fetchfromServerQueue = dispatch_queue_create("fetchfromServer", NULL);
dispatch_async(fetchfromServerQueue, ^{
...
});
dispatch_release(fetchfromServerQueue);
}
You create a queue and give it an async task to do. While that task goes off to do some work you then immediately free the queue. This could cause a few issues if the async task doesn't finish before you release it.
You might want to hold off on the release until after the work in the async call is completed.