Question

I am trying to achive a email like select all functionality in uitableview where on same button tap user can checkmark or remove all checkmark and additionally user can also select/deselect rows(on didSelectRowAtIndexPath). I tried to do but its not working properly, here is my code.

- (IBAction)selectAll:(id)sender
{
    if(myBoolean)
    {
        for (NSInteger s = 0; s < self.iTable.numberOfSections; s++)
        {
            for (NSInteger r = 0; r < [self.iTable numberOfRowsInSection:s]; r++)
            {
                [[self.iTable cellForRowAtIndexPath:[NSIndexPath indexPathForRow:r inSection:s]] setAccessoryType:UITableViewCellAccessoryNone];
            }
        }

        myBoolean = NO;

        [_selectUnselectButton setTitle:@"Select all Friends" forState:UIControlStateNormal];
    }
    else
    {
        for (NSInteger s = 0; s < self.iTable.numberOfSections; s++)
        {
            for (NSInteger r = 0; r < [self.iTable numberOfRowsInSection:s]; r++)
            {
                [[self.iTable cellForRowAtIndexPath:[NSIndexPath indexPathForRow:r inSection:s]] setAccessoryType:UITableViewCellAccessoryCheckmark];
                NSLog(@"%d-%d",s,r);
            }
        }

        myBoolean = YES;

        [_selectUnselectButton setTitle:@"Unselect all Friends" forState:UIControlStateNormal];
    }
}


-(void)tableView:(UITableView *)tableView_ didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    UITableViewCell *cell = [tableView_ cellForRowAtIndexPath:indexPath];

    [cell setSelectionStyle:UITableViewCellSelectionStyleNone];

    if (cell.accessoryType == UITableViewCellAccessoryCheckmark)
    {
        cell.accessoryType = UITableViewCellAccessoryNone;
    }
    else
    {
        cell.accessoryType = UITableViewCellAccessoryCheckmark;
    }
}

Answer 1

Setting the accessory view needs to happen inside the tableView:cellForRowAtIndexPath: method. When you want to change the accessories from outside, the outside method needs to change the model first to indicate that check marks must be placed in certain cells, and then call reloadData on the UITableView.

One way to store what cells are checked is an array of NSIndexSet objects – one index set per section. In the example below I show code for a single section, but you should get an idea of how to make multiple sections work.

// This variable needs to be declared in a place where your data source can get it
NSMutableIndexSet *selected;

// You need to initialize it in the designated initializer, like this:
selected = [[NSMutableIndexSet alloc] init];

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];
    }
    if ([selected containsIndex:indexPath.row]) {
        [cell setAccessoryType:UITableViewCellAccessoryCheckmark];
    } else {
        [cell setAccessoryType:UITableViewCellAccessoryNone];
    }
    // Do the rest of your code
    return cell;
}

Now in the code where you want to set rows selected or unselected you just need to call [selected addIndex:rowToSelect] or [selected removeIndex:rowToUnselect], and call your table’s reloadData.