ViewController.swift

func userDidTapLogin(_ sender: UIButton) {
    sender.startAnimating()
    let command = LoginCommandsFactory.getLoginCommand(id, password: password) {[weak self] (response) in
            self?.handleServerLogin(response)
            sender.stopAnimating()
        }
    do {
      try command.execute()
    }catch{
      sender.stopAnimating()
      showError(error)
    }
}