EXC_BAD_ACCESS - sample code - just need pointing in the right direction

Question

Hi all
I've been trying to add groupins and a floating A-Z listing to my UITableView.
I found a great article on the web but the setup of my code differs slightly (probably because I got some of the architecture wrong to start with!).
Anyhow, I'm getting an EXCBADACCESS error on the following code at this line
NSArray *tempAuthors = [dictionary objectForKey:@"Authors"];
Here's the full function...
-(NSInteger)tableView:(UITableView *)tv numberOfRowsInSection:(NSInteger)section {
NavControllerAppDelegate *appDelegate = (NavControllerAppDelegate *)[[UIApplication sharedApplication] delegate];
NSDictionary *dictionary = [appDelegate.authors objectAtIndex:section];
NSArray *tempAuthors = [dictionary objectForKey:@"Authors"];
return [tempAuthors count];
appDelegate.authors is declared in the interface as follows:-
NSMutableArray *authors;
@property (nonatomic, retain) NSMutableArray *manufacturers;
...and then in the implementation:-
@synthesize authors;
I don't fully understand what the @synthesize or @property does so maybe I've done something wrong here?
Any help much appreciated.
Regards
Wayne

Answer 1

Hi Eric
Here's what I've been able to figure out.
"authors" is a NSMutableArray declared in my AppDelegate. I successfully fill this with NSDictionary objects via a method in the AppDelegate. Each Dictionary object contains the key and the value of each is set to another NSMutableArray of "author" objects.
Using the debugger I can step through and watch the initial "authors" array being built and I can see that at the end of the code it contains 21 objects of type NSDictionary - all good so far.
My code then moves to a UITableViewController where the "numberOfRowsInSection" code is called.
This is where the trouble begins. Stepping through the dbugger once more I can now see that my original "authors" array (which is exposed from the appDelegate as a property) still contains 21 objects however they are now of differing types!!!
Some are still NSDictionary objects but some are wrongly showing as NSObjects - the NSObject ones also have "invalid" in the summary field of the debugger window.
Somehow, the objects which were all created in the same way (via a loop through a database set of records) and added to the "authors" array in the same fashion are now not the same...***?!
Obviously I'm a bit new to all of this but what strikes me is the randomness of the objects in the array which are no longer of the correct type.
btw, let me know what code you would like to see and I shall post it.
Regards
Wayne