private func prepareTextFields() {
    textFields.append(nameTextField)
    textFields.append(surnameTextField)
    textFields.append(addressTextField)
    textFields.append(cityTextField)
    textFields.append(stateTextField)
    textFields.append(zipTextField)
    for tf in textFields {
        tf.delegate = self
    }
}

 func textFieldShouldReturn(_ textField: UITextField) -> Bool {

    if textField == nameTextField {
        textField.resignFirstResponder()
        surnameTextField.becomeFirstResponder()
    } else if textField == surnameTextField {
        textField.resignFirstResponder()
        phoneTextField.becomeFirstResponder()
    } else if textField == addressTextField {
        textField.resignFirstResponder()
        cityTextField.becomeFirstResponder()
    } else if textField == cityTextField {
        textField.resignFirstResponder()
        stateTextField.becomeFirstResponder()
    } else if textField == stateTextField {
        textField.resignFirstResponder()
        zipTextField.becomeFirstResponder()
    } else if textField == zipTextField {
        textField.resignFirstResponder()
    }
    return true
}