func selectedSection(sender: UIButton) {
    let previousSelected = self.selectedSection
    self.selectedSection = sender.tag

    if previousSelected != self.selectedSection {
        // one section opens another gets closed
        // workaround so the animation does not look awful for section headers
        print("Previous: (previousSelected)")
        sectionHeaders[previousSelected].toggleIcon()
        print("Selected: (self.selectedSection)")
        sectionHeaders[self.selectedSection].toggleIcon()
        print("***********")

        var indexPathToInsert = [IndexPath]()
        var indexPathToDelete = [IndexPath]()

        for i in 0..<self.menuItems[self.selectedSection].getSubItems().count {
            indexPathToInsert.append(IndexPath(row: i, section: self.selectedSection))
        }

        for i in 0..<self.menuItems[previousSelected].getSubItems().count {
            indexPathToDelete.append(IndexPath(row: i, section: previousSelected))
        }


        tableView.beginUpdates()
        tableView.deleteRows(at: indexPathToDelete, with: .none)
        tableView.insertRows(at: indexPathToInsert, with: .automatic)
        tableView.endUpdates()
    } else {
        // close the section so the selected section is 0 again
        self.selectedSection = 0

        print("Previous: (previousSelected)")
        sectionHeaders[previousSelected].toggleIcon()
        print("***********")
        tableView.reloadSections([previousSelected], with: .none)
    }
}

func toggleIcon() {
    isOpen = !isOpen
    print("(isOpen)")

    if isOpen {
        print("Works")
        self.sectionIcon.image = UIImage(named: "arrow-up")
    } else {
        print("Does not work")
        self.sectionIcon.image = UIImage(named: "arrow-down")
    }
}

'Selected: 1'
true
Works