To collapse table header in swift ->

1. Make a property of NSMutableSet, name it "collapsedSections", this property will be use to check Collapsed section in the UItableViewCell.

var collapsedSections:NSMutableSet = []

2. Create a header for UITableView and give UIButton tag to the header .

func tableView(tableView: UITableView, viewForHeaderInSection section: Int) -> UIView? {
      let view = UIView(frame: CGRectMake(0, 0, tableView.bounds.size.width, 25))
      view.backgroundColor = UIColor.blackColor().colorWithAlphaComponent(0.9)
        
      let headerLbl = UILabel(frame: CGRectMake(12, 4, tableView.bounds.size.width-12, 18))
      headerLbl.font = UIFont(name: "HelveticaNeue", size: 16)
      headerLbl.tag = 111
      headerLbl.textColor = UIColor.whiteColor()
       if section == 0{
               headerLbl.text = Section1
             }
        else{
               headerLbl.text = Section2
            }
       let btn = UIButton(frame: CGRectMake(0, 0, tableView.bounds.size.width, 25))

// Add action to UIButton
       btn.addTarget(self, action: "tableHeaderTouched:", forControlEvents: UIControlEvents.TouchUpInside)
       btn.tag = section
       view.addSubview(btn)
       view.addSubview(headerLbl)
       return view
    }

3. To Collapse section of UITableView the following method will be trigger .

func tableHeaderTouched(sender : UIButton){
        tableView.beginUpdates()
        var section = Int()
        section = sender.tag
        var shouldCollapse = Bool()
        shouldCollapse = !collapsedSections.containsObject(section)
        var numOfRows = Int()
        var indexPaths = NSArray()
        if shouldCollapse{

// this condition will add row to cell
            numOfRows = self.tableView .numberOfRowsInSection(section)
            indexPaths = self.indexPathsForSection(section, withNumberOfRows: numOfRows)
            self.tableView .deleteRowsAtIndexPaths(indexPaths as! [NSIndexPath], withRowAnimation: UITableViewRowAnimation.Top)
            collapsedSections.addObject(section)
            
        }
        else{

// this condition will delete row from cell
            indexPaths = self.indexPathsForSection(section, withNumberOfRows: numOfRows)
            self.tableView.insertRowsAtIndexPaths(indexPaths as! [NSIndexPath], withRowAnimation: UITableViewRowAnimation.Top)
            collapsedSections.removeObject(section)
        }
        self.tableView .endUpdates()
    }

4. This function will calculate indexPath of section to add/delete the rows in UITableView header .

func indexPathsForSection(section:Int, withNumberOfRows numberOfRows:Int)->NSArray{
        let indexPaths = NSMutableArray()
        var indexPath = NSIndexPath()
        
        var i = Int()
        for i = 0; i < numberOfRows; i++ {
            indexPath = NSIndexPath(forRow: i, inSection: section)
            indexPaths.addObject(indexPath)
        }
        return indexPaths
    }