moveRowAtIndexPath - Moving cells between sections

Question

In my UITableView I have this said relationship `Department -< Employees` (array of names) I have set up custom objects for each model. In my `moveRowAtIndexPath`, I can move in a specific section; however it crashes if I try to move it between sections. The idea being I want to be able to move "Tom" from "Sales" to "Marketing" ``` #pragma mark - UITableView delegate -(NSInteger) numberOfSectionsInTableView:(UITableView *)tableView { return [_objects count]; } -(NSInteger) tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { Department *department = [_objects objectAtIndex:section]; return [department.employees count]; } - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"CellId" forIndexPath:indexPath]; // Configure the cell... Department *department = [_objects objectAtIndex:indexPath.section]; Employee *employee = [department.employees…

Accepted Answer

Your problem is that you have manipulated the data model, but you haven't told the tableview about the changes you made.

Because you call `beginUpdates`/`endUpdates` the tableview is expecting some changes, so after `endUpdates` it calls `numberOfRowsInSection` - which returns the answer '3' - but it is expecting 2+0 (because you didn't tell it about the new row).

You have a couple of options:

1 - Use `moveRowAtIndexPath:toIndexPath:`

```
- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath
{
    if (fromIndexPath != toIndexPath ) {

Department *department = [_objects objectAtIndex:fromIndexPath.section];
        Employee *employee = [department.employees objectAtIndex:fromIndexPath.row];

[tableView beginUpdates];
        [department.employees removeObjectAtIndex:fromIndexPath.row];
        [department.employees insertObject:employee atIndex:toIndexPath.row];
        [tableview moveRowAtIndexPath:fromIndexPath toIndexPath:toIndexPath];
        [self.tableView endUpdates];
    }
}
```

2 - Use reload without the `beginUpdate`/`endUpdate`

```
- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath
{
    if (fromIndexPath != toIndexPath ) {

Department *department = [_objects objectAtIndex:fromIndexPath.section];
        Employee *employee = [department.employees objectAtIndex:fromIndexPath.row];

[department.employees removeObjectAtIndex:fromIndexPath.row];
        [department.employees insertObject:employee atIndex:toIndexPath.row];
        [tableView reloadData];
    }
}
```

moveRowAtIndexPath - Moving cells between sections

Solution

Problem