Question

I have a button on my TableView header that is an empty box, and when pressed, is a checkmark. I have that same button on the cells for that header. So I basically want to perform an action on each cell that is in that section. I’m using the Animating TableView from WWDC 2010 as my example. The header object has an array of integers that keep track of how many rows are in its section.

I’m not really sure from here, how I can get the custom UITableViewCell to perform my action on. Any thoughts? Thanks.

So far I have something like this:

- (void)selectAllCheckmarksInSectionHeaderView:(SectionHeaderView *)sectionHeaderView forSection:(NSInteger)section {
    SectionInfo *sectionInfo = [self.SectionInfoArray objectAtIndex:section];
    int totalRows = [[sectionInfo rowHeights] count];
    for (int row = 0; row < totalRows; row++) {
        NSIndexPath *path = [NSIndexPath indexPathForRow:(NSUInteger)row inSection:section];
        OrderTableViewCell *cell = (OrderTableViewCell *)[_orderTableView cellForRowAtIndexPath:path];
        cell.CheckmarkButton.selected = YES;
    }
}

However my OrderTableViewCell is nil.

Answer 1

To reference a button that is a located in a section header, you’ll have to assign it to an instance variable to keep a reference to it. To obtain references to all of the cells in a section and update them, you’ll want to try something like this…

CGRect sectionRect = [self.tableView rectForSection:0]; // Rect for first section
NSArray *indexPathsInSection = [self.tableView indexPathsForRowsInRect:sectionRect];

for (NSIndexPath *indexPath in indexPathsInSection)
{
    // Obtain the cell at each index path and update its accessory state
    UITableViewCell *cell = [self.tableView cellForRowAtIndexPath:indexPath];
    cell.accessoryType = UITableViewCellAccessoryCheckmark;
}

Of course this is an overly simplistic example. A more flexible approach would be to update some model object when a section is “selected” and reload the table. Then in your -tableView:cellForRowAtIndexPath: you would determine whether a cell in a section should be checkmarked based off the model object for the whole section.