NSButton (checkbox) won't redraw after changing it's state

I'm trying to mark/unmark all the checkboxes in my NSTableView, but they stay untouched when I set state to NSOnState or NSOffState

func tableView(tableView: NSTableView, viewForTableColumn tableColumn: NSTableColumn?, row: Int) -> NSView? {

    switch mode{
    case .Normal:
        let cell = tableView.makeViewWithIdentifier("record", owner:self) as? Record
        cell?.translation.stringValue = ((array[row] as! NSManagedObject).valueForKey("result") as! NSArray)[0] as! String
        cell?.source.stringValue = (array[row] as! NSManagedObject).valueForKey("source") as! String
        return cell
    case .Deletion:
        let cell = tableView.makeViewWithIdentifier("record_del", owner:self) as? RecordDel
        cell?.translation.stringValue = ((array[row] as! NSManagedObject).valueForKey("result") as! NSArray)[0] as! String
        cell?.source.stringValue = (array[row] as! NSManagedObject).valueForKey("source") as! String

        switch automark{
            case .Mark:
                cell?.checkbox.state = NSOnState
            case .Unmark:
                cell?.checkbox.state = NSOffState
            case .None:
                break
        }

        return cell
    }

}

I tried calling cell?.checkbox.cell()?.display() and cell?.checkbox.display() and even cell?.display() but still get no result. Is there a proper way to check a checkbox programmatically?