Retain / Release mistake

Question

I am trying to figure out why I am getting EXC_BAD_ACESS by this code. I have no clu. Can anyone help me pls.

- (void)loadJsonFile:(NSString*)fileName {
    NSError *error = nil;
    NSData *jsonData = [[[NSString alloc]
                         initWithContentsOfFile:[[NSBundle mainBundle]
                                                 pathForResource:fileName ofType:@"json"]
                         encoding:NSUTF8StringEncoding error:&error]
                        dataUsingEncoding:NSUTF8StringEncoding];
    
    jsonDic = [[NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableContainers error:&error] retain];
   [jsonData release];
}

If I am commenting out the "[jsonData release];" line, everything functions. But why ? I allocate jsonData, fill it with data and pass it to NSJSONSerialization for getting the jsonDic. After I have the serialization, I release the jsonData and want to use the jsonDic, however some time after the "[jsonData release];" I am getting "EXC_BAD_ACCESS" Exception.

I have no clu, any help appreciated.

Answer 1

You release jsonData, but you never retained it. The static analyzer (Menu "Product" ➞ "Analyze") would have shown you this problem. Also, you're not releasing the NSString you're allocating.

Do it like this:

- (void)loadJsonFile:(NSString*)fileName {
    NSError *error = nil;
    NSData *jsonData = [[[[[NSString alloc]
                         initWithContentsOfFile:[[NSBundle mainBundle]
                                                 pathForResource:fileName ofType:@"json"]
                         encoding:NSUTF8StringEncoding error:&error] autorelease]
                        dataUsingEncoding:NSUTF8StringEncoding] retain];

    jsonDic = [[NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableContainers error:&error] retain];
    [jsonData release];
}

You might want to consider using ARC (Automatic Reference Counting). Xcode can convert your project almost completely automatically with Menu "Edit" ➞ "Refactor" ➞ "Convert to Objective-C ARC…". There are only few reasons to keep managing memory manually.