Problem with sectioning UITableViewController - iphone

Question

I have a class that extends UITableviewController which displays a data type called "GigData" (which only contains strings for now). The content is stored in "data" which is an NSMutableArray containing NSMutableArrays containing "GigData". This array is passed to the instance of my class and the arrays inside arrays make up the sections of the table. Here is the code I have implemented so far:
#synthesize data = _data;
- (id)init
{
self = [super initWithStyle:UITableViewStyleGrouped];
_data = [[NSMutableArray alloc] init];
[[self navigationItem] setTitle:#"Gigs by Date"];
return self;
}
- (id)initWithStyle:(UITableViewStyle)style
{
return [self init];
}
- (void)didReceiveMemoryWarning
{
// Releases the view if it doesn't have a superview.
[super didReceiveMemoryWarning];
// Release any cached data, images, etc that aren't in use.
}
#pragma mark - View lifecycle
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
// Return YES for supported orientations
return (interfaceOrientation == UIInterfaceOrientationPortrait);
}
#pragma mark - Table view data source
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
// Return the number of sections.
return [_data count];
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
// Return the number of rows in the section.
return [[_data objectAtIndex:section] 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] autorelease];
}
NSMutableArray *sectionArray = [_data objectAtIndex:[indexPath section]];
GigData *gig =[sectionArray objectAtIndex:[indexPath row]];
[[cell textLabel] setText:[gig description]];
return cell;
}
- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section
{
GigData *temp = [[_data objectAtIndex:section] objectAtIndex:0];
return [temp date];
}
When I run the app, I can see everything sorted into the right groups and all the displays are correct, except for the final section, which keeps changing names, some of which have included "cs.lproj", "headers" and "method not allowed". Scrolling to the bottom of the table then towards the top crashes the app. Also, if I provide my own implementation for description for "GigData", the app crashes even worse, I cannot scroll to the second section at all. Data is declared as a property in the header file and is set to nonatomic and retain. I have also tried using the code inside the init method to create the data array inside this class, but this makes no difference. Some runnings of the app have said there is a problem in tableView:cellForRowAtIndexPath: when I create "sectionArray". Has any body got any suggestions as to what I am doing wrong?