Question

Getting error: *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSNull isEqualToString:]: unrecognized selector sent to instance'…

The SIGABRT came on the else cell.textLabel.text = @"Blank"; line of:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {UITableViewCell *cell = nil;
    static NSString *CellIdentifier = @"Cell";
    cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
         cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier] autorelease];
    }
     NSManagedObjectContext *context = [self managedObjectContext];
     NSEntityDescription *entity = [NSEntityDescription entityForName:@"Pattern" inManagedObjectContext:context];
 // Edit the sort method.
     NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"patternName" ascending:YES selector:@selector(localizedCaseInsensitiveCompare:)];
      NSArray *sortDescriptors = [[[NSArray alloc] initWithObjects:sortDescriptor, nil] autorelease];

     NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
     [fetchRequest setSortDescriptors:sortDescriptors];
     [fetchRequest setEntity:entity];    
     _patterns = [context executeFetchRequest:fetchRequest error:nil];
     [fetchRequest release];
     NSArray *names = [_patterns valueForKey:@"patternName"];
     NSArray *urls = [_patterns valueForKey:@"patternUrl"];

     if (names!= nil) {
        cell.textLabel.text = [names objectAtIndex:indexPath.row];           
     }
     else cell.textLabel.text = @"Blank";
     cell.detailTextLabel.text = [urls objectAtIndex:indexPath.row];
     cell.accessoryType = UITableViewCellAccessoryDetailDisclosureButton;
     return cell;
 }

I can add a defined record (copies the url of the page the user is viewing inserting the URL into both the url field and the name attributes). Editing or creating a new record pops a ModalViewController that presents (for existing records) and captures data in textfields (for new records). Selecting the save crashes, changes only the record of the last-added defined record even if it has been edited and adds that as a new record, keeping the old one. I think somethings wrong with my keeping track of the number of cells.

Any suggestions would be most appreciated.

Answer 1

What you get from executeFetchRequest is array of objects not attributes. You need to loop through array of objects and get attributes from each of them

This

_patterns = [context executeFetchRequest:fetchRequest error:nil];
     [fetchRequest release];
     NSArray *names = [_patterns valueForKey:@"patternName"];
     NSArray *urls = [_patterns valueForKey:@"patternUrl"];

     if (names!= nil) {
        cell.textLabel.text = [names objectAtIndex:indexPath.row];           
     }

Should become

_patterns = [context executeFetchRequest:fetchRequest error:nil];
     [fetchRequest release];


     if (names!= nil) {
        cell.textLabel.text = [[_patterns objectAtIndex:indexPath.row] valueForKey:@"patternName"];           
     }