title: How to get the section when press a button in my custom section header view in tableview
body: <pre><code>func tableView(tableView: UITableView, viewForHeaderInSection section: Int) -&gt; UIView? {
      var sectionHeaderView = NSBundle.mainBundle().loadNibNamed("PlanCellSectionHeader", owner: nil, options: nil).first as PlanCellSectionHeader!
      sectionHeaderView.addBtn.addTarget(self, action: "didPressAdd:", forControlEvents: UIControlEvents.TouchUpInside)
      return sectionHeaderView
  }
  func didPressAdd(sender:UIButton) {
      var point = sender.convertPoint(CGPointZero, toView: self.tableView!)
      var indexPath = self.tableView.indexPathForRowAtPoint(point)
      //won't work
      println("section = \(indexPath?.section)")
  }
  </code></pre>
  
  <p>And it turns out that the indexPath is nil, and when using tags added to each section header, i found that others say it would crash if we delete sections in runtime, so any helps?</p>