TableViewController.swift - From "Expandable and dynamic sized Table Header View and Table Footer View" @ medium.com

TableViewController.swift

//
//  TableViewController.swift
//

import UIKit

// ...

final class TableViewController: UITableViewController {

   // ...

    private let headerView = TableHeaderView()
    private let footerView = TableFooterView()

    override func viewDidLoad() {
        super.viewDidLoad()

        tableView.tableHeaderView = headerView
        tableView.tableFooterView = footerView

        headerView.addGestureRecognizer(
            UITapGestureRecognizer(
                target: self,
                action: #selector(toggleExpandedHeaderView)
            )
        )

        // ...

        tableView.layoutIfNeeded() // To make sure the UITableView's layout includes an up to date TableHeaderView.
    }

    @objc private func toggleExpandedHeaderView() {
        tableView.performBatchUpdates {

            let oldHeaderHeight = headerView.frame.height

            // 0.3 is an educated guess about the duration of UITableView's own update animation duration.
            UIView.animate(withDuration: 0.3) {
                self.headerView.expanded = !self.headerView.expanded

                self.tableView.layoutIfNeeded()

                let newHeaderHeight = self.headerView.frame.height

                // Animate the footer's center along the header's size change.
                self.footerView.center.y += newHeaderHeight - oldHeaderHeight
            }
        }
    }

    // ...

}