Estou tentando criar células expansíveis usando a combinação deUITableViewAutomaticDimension altura da linha e Reprodução automática das células. Para simplificar, comecei com o seguinte código simples, que esperava funcionar:

import UIKit

class ViewController: UITableViewController {

    let cells = [Cell(), Cell(), Cell()]

    override func viewDidLoad() {
        super.viewDidLoad()
        tableView.rowHeight = UITableViewAutomaticDimension
        tableView.estimatedRowHeight = 50

        for cell in cells {
            cell.tableView = tableView
        }
    }

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

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return 3
    }

    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        return cells[indexPath.row]
    }
}

class Cell: UITableViewCell {

    var cons: NSLayoutConstraint?
    var tableView: UITableView?

    init() {
        super.init(style: .default, reuseIdentifier: nil)

        let button = UIButton()
        contentView.addSubview(button)
        button.addTarget(self, action: #selector(Cell.tapped(_:)), for: .touchUpInside)
        button.setTitle("Press me", for: .normal)
        button.setTitleColor(.red, for: .normal)

        button.translatesAutoresizingMaskIntoConstraints = false

        // constraining the button to the view, so that buttons height would define cell height
        let constraints = [
            button.topAnchor.constraint(equalTo: contentView.topAnchor),
            button.rightAnchor.constraint(equalTo: contentView.rightAnchor),
            button.bottomAnchor.constraint(equalTo: contentView.bottomAnchor),
            button.leftAnchor.constraint(equalTo: contentView.leftAnchor),
        ]

        NSLayoutConstraint.activate(constraints)
        cons = button.heightAnchor.constraint(equalToConstant: 100)
        cons?.isActive = true
    }

    func tapped(_ sender: UIButton) {
        // change the height of the button, thus of the contentView too (since the button is constrained to the contentView)
        if cons?.constant == 100 {
            cons?.constant = 200
        } else {
            cons?.constant = 100
        }
        // tell the tableView to redraw itself to apply the change
        tableView?.beginUpdates()
        tableView?.setNeedsDisplay()
        tableView?.endUpdates()
    }

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

Agora isso parece estar funcionando, no entanto, ainda receboUIViewAlertForUnsatisfiableConstraints aviso com a seguinte mensagem:

(
"<NSLayoutConstraint:0x17408c7b0 V:|-(0)-[UIButton:0x109e10290'Press me']   (active, names: '|':UITableViewCellContentView:0x109e0fd90 )>",
"<NSLayoutConstraint:0x17408c8a0 UIButton:0x109e10290'Press me'.bottom == UITableViewCellContentView:0x109e0fd90.bottom   (active)>",
"<NSLayoutConstraint:0x17408c990 UIButton:0x109e10290'Press me'.height == 200   (active)>",
"<NSLayoutConstraint:0x17408db10 'UIView-Encapsulated-Layout-Height' UITableViewCellContentView:0x109e0fd90.height == 100   (active)>"
)

 Will attempt to recover by breaking constraint 
 <NSLayoutConstraint:0x17408c990 UIButton:0x109e10290'Press me'.height == 200   (active)>

Parece que a altura estimada (ou atual) da linha colide com a restrição de autolayout fornecida por mim. Ainda assim, atualizar o tableView usando o código a seguir exibirá como esperado:

tableView?.beginUpdates()
tableView?.setNeedsDisplay()
tableView?.endUpdates()

Como removo o aviso?

Estou ciente de que a simples alteração da prioridade da restrição de altura para 999 removerá o aviso, mas me parece um hack removê-lo, não uma solução. Se eu estiver enganado, por favor, explique. Obrigado.