Question

This is my code (from a Core Data tutorial):

[eventsArray insertObject:event atIndex:0];

NSIndexPath *indexPath = [NSIndexPath indexPathForRow:0 inSection:0];

[self.tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];

[self.tableView scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0] atScrollPosition:UITableViewScrollPositionTop animated:YES];

The third line throws an exception:

2011-05-12 13:13:33.740 Locations[8332:207] *** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[NSMutableArray objectAtIndex:]: index 0 beyond bounds for empty array'
*** Call stack at first throw:
(
    0   CoreFoundation                      0x010145a9 __exceptionPreprocess + 185
    1   libobjc.A.dylib                     0x01168313 objc_exception_throw + 44
    2   CoreFoundation                      0x0100a0a5 -[__NSArrayM objectAtIndex:] + 261
    3   UIKit                               0x0010d5b3 -[UITableView(_UITableViewPrivate) _endCellAnimationsWithContext:] + 6156
    4   UIKit                               0x000fcd36 -[UITableView insertRowsAtIndexPaths:withRowAnimation:] + 56
    5   Locations                           0x00003462 -[RootViewController addEvent] + 690

I’m new to iPhone development, and I can’t understand that does it mean. I’m inserting at the zero index of a tableView, so I have no idea why does not it work with an empty array. Please clarify this to me

---

eventsArray is an array I populate table view from (probably. at least it is used in cellForRowAtIndexPath)

---

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

    // A date formatter for the time stamp.
    static NSDateFormatter *dateFormatter = nil;
    if (dateFormatter == nil) {
        dateFormatter = [[NSDateFormatter alloc] init];
        [dateFormatter setTimeStyle:NSDateFormatterMediumStyle];
        [dateFormatter setDateStyle:NSDateFormatterMediumStyle];
    }

    // A number formatter for the latitude and longitude.
    static NSNumberFormatter *numberFormatter = nil;
    if (numberFormatter == nil) {
        numberFormatter = [[NSNumberFormatter alloc] init];
        [numberFormatter setNumberStyle:NSNumberFormatterDecimalStyle];
        [numberFormatter setMaximumFractionDigits:3];
    }

    static NSString *CellIdentifier = @"Cell";

    // Dequeue or create a new cell.
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier] autorelease];
    }

    Event *event = (Event *)[eventsArray objectAtIndex:indexPath.row];

    cell.textLabel.text = [dateFormatter stringFromDate:[event creationDate]];

    NSString *string = [NSString stringWithFormat:@"%@, %@",
                        [numberFormatter stringFromNumber:[event latitude]],
                        [numberFormatter stringFromNumber:[event longitude]]];
    cell.detailTextLabel.text = string;

    return cell;
}

Answer 1

Had the same problem. Just need to tell the tableview that it has 1 section to add too. It defaults to 0 if you don’t update it.

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    // Return the number of sections.
    return 1;
}