FCViewController.swift

func fetchConfig() {
    var expirationDuration: Double = 3600
    // If in developer mode cacheExpiration is set to 0 so each fetch will retrieve values from
    // the server.
    if (self.remoteConfig.configSettings.isDeveloperModeEnabled) {
      expirationDuration = 0
    }

    // cacheExpirationSeconds is set to cacheExpiration here, indicating that any previously
    // fetched and cached config would be considered expired because it would have been fetched
    // more than cacheExpiration seconds ago. Thus the next fetch would go to the server unless
    // throttling is in progress. The default expiration duration is 43200 (12 hours).
    remoteConfig.fetch(withExpirationDuration: expirationDuration) { (status, error) in
      if (status == .success) {
        print("Config fetched!")
        self.remoteConfig.activateFetched()
        let friendlyMsgLength = self.remoteConfig["friendly_msg_length"]
        if (friendlyMsgLength.source != .static) {
          self.msglength = friendlyMsgLength.numberValue!
          print("Friendly msg length config: \(self.msglength)")
        }
      } else {
        print("Config not fetched")
        print("Error \(error)")
      }
    }
  }