Question

I’m trying to setup my table so that the user can select one item per section.

For example:

- Section 0
    - Row 0 √
    - Row 1
- Section 1
    - Row 0
    - Row 1 √
    - Row 2

So in the above example if the user selects section 0, row 1 then row 0 in the same section should be unchecked and the selected row gets a checkmark.

Same goes for section 1 where any selected row should get a checkmark and then I want to remove the checkmark from the previously selected row in the same section.

- Section 0
    - Row 0
    - Row 1 √
- Section 1
    - Row 0
    - Row 1
    - Row 2 √

Please keep in mind that I won’t have a predefined number of sections or rows, so the code should work for this scenario. Here’s what I currently have, hopefully that might get me started on the right path.

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    [self.tableView deselectRowAtIndexPath:indexPath animated:YES];
    MyObject *myObject = [self.fetchedResultsController objectAtIndexPath:indexPath];
    UITableViewCell *cell = [self.tableView cellForRowAtIndexPath:indexPath];
    if ([myObject.optionSelected boolValue] == NO) {
        [myObject setOptionSelected:[NSNumber numberWithBool:YES]];
        [cell setAccessoryType:UITableViewCellAccessoryCheckmark];
    } else {
        [myObject setOptionSelected:[NSNumber numberWithBool:NO]];
        [cell setAccessoryType:UITableViewCellAccessoryNone];
    }
    if ([tableView numberOfRowsInSection:indexPath.section] > 1) {
        NSMutableArray *cells = [[NSMutableArray alloc] init];
        for (NSInteger i = 0; i < [tableView numberOfRowsInSection:indexPath.section]; ++i) {
            [cells addObject:[tableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:i inSection:indexPath.section]]];
        }
        for (UITableViewCell *deselectCell in cells) {
            if ([self.tableView indexPathForCell:deselectCell] != indexPath && deselectCell != cell) {
                MyObject *tempObject = [self.fetchedResultsController objectAtIndexPath:[self.tableView indexPathForCell:deselectCell]];
                [tempObject setOptionSelected:[NSNumber numberWithBool:NO]];
                [cell setAccessoryType:UITableViewCellAccessoryNone];
            }
        }
    }
}

As you can see I am also setting the object’s selected state, I’d like this to remain intact 🙂

Thanks for any feedback and help in advance!

Answer 1

Your tableview should declare a mutable array to hold the currently selected paths:

NSMutableArray *selectedCellPaths = [[NSMutableArray alloc] init];

Then your tableView:didSelectRowAtIndexPath: should look like this

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    [self.tableView deselectRowAtIndexPath:indexPath animated:YES];
    MyObject *myObject = [self.fetchedResultsController objectAtIndexPath:indexPath];
    UITableViewCell *cell = [self.tableView cellForRowAtIndexPath:indexPath];
    if ([myObject.optionSelected boolValue] == NO) {
        [myObject setOptionSelected:[NSNumber numberWithBool:YES]];
        [cell setAccessoryType:UITableViewCellAccessoryCheckmark];
        [selectedCellPaths addObject:indexPath];
    } else {
        [myObject setOptionSelected:[NSNumber numberWithBool:NO]];
        [cell setAccessoryType:UITableViewCellAccessoryNone];
        if ([selectedCellPaths containsObject:indexPath]) {
            [selectedCellPaths removeObject:indexPath];
        }
    }

    // Now we're going to remove all but the cell path that is actually selected.

    NSMutableArray *cellsToRemove = [[NSMutableArray alloc] init];
    for (NSIndexPath *selectedCellIndexPath in selectedCellPaths) {
        if ([selectedCellIndexPath compare:indexPath] != NSOrderedSame && selectedCellIndexPath.section == indexPath.section) {
        // deselect cell at selectedCellPath
            [cellsToRemove addObject:selectedCellIndexPath];
        }
    }
    [selectedCellPaths removeObjectsInArray:cellsToRemove];
}

Note I have just put in a comment where you would want to deselect the actual cell at the cell path that is not selected. You need to fill that code in yourself.

I haven’t tested this code, just modified what you had in TextMate but it should work barring minor changes.