UITextField in custom UITableViewCell unexpectedly

I have a TableView with custom cells that have a TextField inside, unfortunately I get a Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value when I use them (press return or touch the screen outside the textField to get out of the placeholder).

Here is my code :

class WalletTableViewController: UIViewController, UITextFieldDelegate {

    var cryptosArray: [Cryptos] = []

    override func viewDidLoad() {
        super.viewDidLoad()

        tableView.delegate = self

        loadCryptoArray()
    }

    func loadCryptoArray() {

        if UserDefaults.standard.object(forKey: "cryptosArray") != nil {
            if let decoded = UserDefaults.standard.object(forKey: "cryptosArray") as? Data? {
               let decodedCryptoArray = NSKeyedUnarchiver.unarchiveObject(with: decoded!) as! [Cryptos]
               cryptosArray = decodedCryptoArray
        }
    } 
}

}

The TableView extension :

extension WalletTableViewController: UITableViewDelegate, UITableViewDataSource {

    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return cryptosArray.count
    }
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

        let crypto = cryptosArray[indexPath.row]

        let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath) as! WalletTableViewCell
        cell.setCrypto(crypto: crypto)
        cell.delegate = self
        cell.amountTextField.delegate = self

        return cell
    }
    func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
        return 85
    }
    func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
        if editingStyle == .delete {
            cryptosArray.remove(at: indexPath.row)
            tableView.deleteRows(at: [indexPath], with: .fade)

            let userDefaults = UserDefaults.standard
            let encodedData : Data = NSKeyedArchiver.archivedData(withRootObject: cryptosArray)
            userDefaults.set(encodedData, forKey: "cryptosArray")
            userDefaults.synchronize()
        }
    }
}

This is the delegate function for the TextField:

extension WalletTableViewController: CryptoCellDelegate {
    func cellAmountEntered(_ sender: Any) {
        if WalletTableViewCell().amountTextField.text == "" {
            return
        }
        let str = WalletTableViewCell().amountTextField.text

        let formatter = NumberFormatter()
        formatter.locale = Locale(identifier: "en_US")
        let dNumber = formatter.number(from: str!)
        let nDouble = dNumber!
        let eNumber = Double(truncating: nDouble)

        WalletTableViewCell().amountLabel.text = String(format:"%.8f", eNumber)

      UserDefaults.standard.set(WalletTableViewCell().amountLabel.text, forKey: "bitcoinAmount")
        WalletTableViewCell().amountTextField.text = ""

    }
}

The custom cell file :

protocol CryptoCellDelegate {
    func cellAmountEntered(_ sender: Any)
}

class WalletTableViewCell: UITableViewCell {

    @IBOutlet weak var cryptoNameLabel: UILabel!
    @IBOutlet weak var amountLabel: UILabel!

    @IBOutlet weak var amountTextField: UITextField!

    var cryptoItem: Crypto!
    var delegate: CryptoCellDelegate?

    func setCrypto(crypto: Cryptos) {

        cryptoNameLabel.text = crypto.name
    }

    @IBAction func amountTextFieldEntered(_ sender: Any) {
        delegate?.cellAmountEntered((Any).self)
    }

}

The TableView has as many cells as the user wants, so this is depending on the array of objects that create the cells.

I guess I have a delegate problem somewhere? I am quite new to UITableView so this has been quite a challenge, forgive any stupid blunder :)

PS: I've tried to keep the code short by removing keyboard functions and unrelated stuff, please tell me if you need something else.

Everywhere where you use WalletTableViewCell() you are creating a new instance of the WalletTableViewCell. The crash happens because you are creating it programmatically, while WalletTableViewCell was designed using storyboards, and since you did not instantiated it using storyboards, @IBOutlets have not been set, therefore are nil.

Update

Try to fix it using this. Update CryptoCellDelegate to this:

protocol CryptoCellDelegate {
    func cellAmountEntered(_ walletTableViewCell: WalletTableViewCell)
}

Then in WalletTableViewCell update amountTextFieldEntered to:

@IBAction func amountTextFieldEntered(_ sender: Any) {
    delegate?.cellAmountEntered(self)
}

And finally update delegate implementation:

extension WalletTableViewController: CryptoCellDelegate {
    func cellAmountEntered(_ walletTableViewCell: WalletTableViewCell) {
        // now you can use walletTableViewCell to access the cell that called the delegate method
        if walletTableViewCell.amountTextField.text == "" {
            return
        }
        let str = walletTableViewCell.amountTextField.text

        let formatter = NumberFormatter()
        formatter.locale = Locale(identifier: "en_US")
        let dNumber = formatter.number(from: str!)
        let nDouble = dNumber!
        let eNumber = Double(truncating: nDouble)

        walletTableViewCell.amountLabel.text = String(format:"%.8f", eNumber)

        UserDefaults.standard.set(walletTableViewCell.amountLabel.text, forKey: "bitcoinAmount")
        walletTableViewCell.amountTextField.text = ""

    }
}