// TimeInterval is set to expirationDuration here, indicating the next fetch request will use
// data fetched from the Remote Config service, rather than cached parameter values, if cached
// parameter values are more than expirationDuration seconds old. See Best Practices in the
// README for more information.
remoteConfig.fetch(withExpirationDuration: TimeInterval(expirationDuration)) { (status, error) -> Void in
  if status == .success {
    print("Config fetched!")
    self.remoteConfig.activate(completionHandler: { (error) in
      // ...
    })
  } else {
    print("Config not fetched")
    print("Error: \(error?.localizedDescription ?? "No error available.")")
  }
  self.displayWelcome()
}