NSRangeException in didSelectRowAtIndexPath for iPad app - xcode

Question

Working on an app that populates a table based on clicking on a cell from another table. So, I click on the (table named)Recipe, and an second table (Ingredients) is populated. I'm pulling the data from a sqlite DB using core data. When I select the first recipe, the ingredients populate no problem. Selecting any other recipe results in the NSRangeException error.
Code:
- (void)tableView:(UITableView*)aTableView didSelectRowAtIndexPath:(NSIndexPath*)indexPath
{
UITableViewCell *cell = (UITableViewCell *)[(UITableView *)srcTableView cellForRowAtIndexPath:indexPath];
NSLog(#"didSelectRowAtIndexPath: row=%i",indexPath.row);
MealPlanItAppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
NSManagedObjectContext *context = [appDelegate managedObjectContext];
NSEntityDescription *entityDesc = [NSEntityDescription entityForName:#"Ingredients" inManagedObjectContext:context];
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:entityDesc];
NSLog(#"Cell: %#", cell.textLabel.text);
NSPredicate *pred = [NSPredicate predicateWithFormat:#"(RecipeID = %#)", cell.textLabel.text];
[request setPredicate:pred];
NSManagedObject *matches = nil;
NSError *error;
NSArray *objects = [context executeFetchRequest:request error:&error];
if ([objects count] == 0)
{
NSLog(#"No matches");
dtlData = [[NSMutableArray alloc] initWithArray:nil];
[dtlTableView reloadData];
} else {
NSLog(#"Match found");
dtlData = [[NSMutableArray alloc] initWithArray:nil];
[dtlTableView reloadData];
matches = [objects objectAtIndex:0];
for(matches in objects)
{
[dtlData insertObject:[matches valueForKey:#"Ingredient"] atIndex:indexPath.row];
[dtlTableView insertRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
[dtlTableView reloadData];
}
}
[request release];
}
It explodes at the line near the end:
[dtlData insertObject:[matches valueForKey:#"Ingredient"] atIndex:indexPath.row];
with an error: * Terminating app due to uncaught exception 'NSRangeException', reason: '* -[__NSArrayM insertObject:atIndex:]: index 4 beyond bounds for empty array'
Where the index 4 is the 4th cell clicked...so it always corresponds with the cell row.
Using the NSLog, the data is returned by the call and returned into 'objects' with the appropriate counts.
And, like I said, it works when clicking the first cell but no other cell. I can click multiple times on the first cell and it continues working. So, it has something to do with the 0 index (I suspect) but can't figure what.
If I replace the line
[dtlData insertObject:[matches valueForKey:#"Ingredient"] atIndex:indexPath.row];
with
[dtlData insertObject:[matches valueForKey:#"Ingredient"] atIndex:0];
I get the exact same behavior.
Any thoughts?

Answer 1

Nothing is wrong with the UITable View Code (as i had a quick look over that, just wondering why are you allocating the Array on every click of the table view cell? Initialize the array once, and handle add or removal of objects appropriately). Anyways, coming to your question : The issue is due to using
[array insertobject:]
The reason is that the array is initialized by a NILL object and when you try to insert object at index n, it complaints that the array is empty as the indexes < n are all NIL. So instead of using [array insertobject:atindex:], i would suggest you to simply call [array addobject:] this will add the objects at consecutive locations and will resolve the crash.