MoveRowAtIndexPath: how to delete a section after wrapping the last row in another section

Question

I have a table view with several sections. I would like to be able to move rows from one section to another and delete a section when it has no rows. I am trying to do this with moveRowAtIndexPath, but the code I have does not work and throws an NSRangeException.

Here is a sample code:

- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath {

    NSUInteger fromSection = [fromIndexPath section];
    NSUInteger fromRow = [fromIndexPath row];
    NSString *fromKey = [self.keys objectAtIndex:fromSection];
    NSMutableArray *fromEventSection = [self.eventsDict objectForKey:fromKey];

    NSUInteger toSection = [toIndexPath section];
    NSUInteger toRow = [toIndexPath row];
    NSString *toKey = [self.keys objectAtIndex:toSection];
    NSMutableArray *toEventSection = [self.eventsDict objectForKey:toKey];

    id object = [[fromEventSection objectAtIndex:fromRow] retain];
    [fromEventSection removeObjectAtIndex:fromRow];
    [toEventSection insertObject:object atIndex:toRow];
    [object release];
    // The above code works just fine!

    // Try to delete an empty section. Here is where trouble begins:
    if ((fromSection != toSection) && [fromEventSection count] == 0) {
        [self.keys removeObjectAtIndex:fromSection];
        [self.eventsDict removeObjectForKey:fromKey];

        [tableView deleteSections:[NSIndexSet indexSetWithIndex:fromSection] withRowAnimation:UITableViewRowAnimationFade];
    }

Answer 1

I was fortunate enough to execute the deleteSections method in a block after the end of the moveRowAtIndexPath method, wrapping the delete in dispatch_async.

    dispatch_async(dispatch_get_main_queue(), ^{
        if ((fromSection != toSection) && [fromEventSection count] == 0) {
            [self.keys removeObjectAtIndex:fromSection];
            [self.eventsDict removeObjectForKey:fromKey];
            [tableView deleteSections:[NSIndexSet indexSetWithIndex:fromSection] withRowAnimation:UITableViewRowAnimationFade];
        }
    });

Answer 2

. .

- , :

- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath {
    NSInteger beforeSectionCount = [store sectionCount];
    [store moveObject:fromIndexPath toIndexPath:toIndexPath];
    if (beforeSectionCount > [store sectionCount]
        [self performSelector:@selector(deleteSection:) withObject:fromIndexPath: afterDelay:0.2]
}

- (void)deleteSection:(NSIndexPath *)indexPath {
    [[self tableView] beginUpdates];
    [[self tableView] deleteSections:[NSIndexSet indexSetWithIndex:[indexPath section]]
                withRowAnimation:UITableViewRowAnimationFade];
    [[self tableView] endUpdates];
}