Expandable TableView

import UIKit

class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {

    @IBOutlet var tableView: UITableView!    
    
    var headerView = UIView()    
    var selectedSections = NSMutableArray()
    
    override func viewDidLoad() {
        super.viewDidLoad()
//        self.tableView.reloadData()
        // Do any additional setup after loading the view, typically from a nib.
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    func numberOfSections(in tableView: UITableView) -> Int {
        return 3
    }
    
    func tableView(_ tableView: UITableView, heightForHeaderInSection section: Int) -> CGFloat {
        return 60
    }
    
    func tableView(_ tableView: UITableView, viewForHeaderInSection section: Int) -> UIView? {
        headerView = UIView(frame: CGRect(x: 0, y: 0, width: self.tableView.frame.size.width, height: 50))
        headerView.backgroundColor = UIColor.orange
        headerView.tag = section
        headerView.isUserInteractionEnabled = true
        
        headerView.addGestureRecognizer(UITapGestureRecognizer(target: self, action: (!self.selectedSections.contains(section)) ? #selector(self.expand(sender:)) : #selector(self.collapse(sender:))))
        
        return headerView
    }
    
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return self.selectedSections.contains(section) ? 2 : 0
    }
    
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell:UITableViewCell = tableView.dequeueReusableCell(withIdentifier: "cell")!
        cell.textLabel?.text = "Row \(indexPath.row)"
        
        return cell
    }
    
    func expand(sender:UIGestureRecognizer){
        self.selectedSections.add(sender.view!.tag)
        self.tableView.reloadSections([sender.view!.tag], with: .automatic)
    }
    
    func collapse(sender:UIGestureRecognizer){
        self.selectedSections.remove(sender.view!.tag)
        print(self.selectedSections)
        self.tableView.reloadSections([sender.view!.tag], with: .automatic)
    }
    
}