Reloading NSTableView data from a AFNetworking callback - objective-c

Question

Edit: as it turned out I was going completely the wrong way with this. I discovered that when I tried to wire a button to call a method on the controller, it still crashed, even when that controller action did absolutely nothing. This led me to wonder, and I realized in my main window controller, I was creating another controller and then moving on with no references to that new controller. So essentially my crash was due to the view controller being deallocated, not anything to do with reloading the table or fetching data. I've solved this by adding a strong property for the child view controller in the main window controller, though I'm not sure this is 100% the best strategy.
Driving me slightly batty here... I'm trying to do an AFNetworking call and reload an NSTable when I get the results. This, however, crashes with rather unhelpful errors. I am guessing that this is due to a threading issue, but various methods I've tried to avoid this (such as using __block) haven't helped. I'm at a loss as to how to get this to work.
Here is the hopefully trimmed down relevant code.
// Controller.h
#property (strong, nonatomic) NSMutableArray *messages;
// Controller.m
#synthesize messages = _messages;
- (id)initWithNibName:(NSString *)nibNameOrNil room: (Room *) theRoom bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
_messages = [[NSMutableArray alloc] init];
}
}
- (void)loadView {
[super loadView];
[self updateData];
}
- (void) updateData {
...
[manager GET:url parameters:nil success:^(AFHTTPRequestOperation *operation, id responseObject) {
NSArray *responseObjs = responseObject[#"messages"];
for (NSDictionary *message in responseObjs) {
Message *m = [[Message alloc] init];
m.property = message[#"property];
...
[_messages addObject: m];
}
[messagesTableView reloadData];
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
NSLog(#"Error: %#", error);
}];
}
- (NSInteger) numberOfRowsInTableView:(NSTableView *)tableView {
return [_messages count];
}
- (NSView *) tableView: (NSTableView *) tableView viewForTableColumn: (NSTableColumn *) tableColumn row:(NSInteger) row {
NSTableCellView *cellView = [tableView makeViewWithIdentifier:#"MainCell" owner: self];
[cellView.textField setStringValue: #"foo"];
return cellView;
}
The error I'm getting is: Thread 1: EXC_BAD_ACCESS (code=EXC_i386_GPFLT)
Any clues? If I skip the reloadData call then it runs without crashing, though obviously shows no data.