CellExpansion

import UIKit
import PlaygroundSupport

final class ViewController: UITableViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        tableView.register(TableViewCell.self, forCellReuseIdentifier: "\(TableViewCell.self)")
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        perform(#selector(self.toggleExpanded), with: nil, afterDelay: 1.0)
    }

    override func numberOfSections(in tableView: UITableView) -> Int {
        return 1
    }

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return 1
    }

    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "\(TableViewCell.self)", for: indexPath)
        cell.backgroundColor = .blue
        return cell
    }

    @objc
    private func toggleExpanded() {
        tableView.beginUpdates()
        tableView.visibleCells.flatMap { $0 as? TableViewCell }.forEach { $0.isExpanded = !$0.isExpanded }
        tableView.endUpdates()
        perform(#selector(self.toggleExpanded), with: nil, afterDelay: 2.0)
    }
}

final class TableViewCell: UITableViewCell {

    var isExpanded: Bool = false {
        didSet {
            heightConstraint.constant = isExpanded ?  150 : 75
        }
    }

    lazy var heightConstraint = self.heightAnchor.constraint(equalToConstant: 75)

    override init(style: UITableViewCellStyle, reuseIdentifier: String?) {
        super.init(style: style, reuseIdentifier: reuseIdentifier)
        heightConstraint.isActive = true
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

PlaygroundPage.current.liveView = ViewController()