I'm struggling to figure out the best approach to get an alert to present with my current code

I'm wanting to present an alert message when a user doesn't have network connection.

I have a function that will make an API call for data and also checking if there is network connectivity to avoid a crash. I'm sort of stuck on the best approach from here.

Code Block    
func getRoutes(completion: @escaping ([Route]) -> ()) { //Post is data model
        let routeMonitor = NWPathMonitor()
        print("aMonitor is set")
        routeMonitor.pathUpdateHandler = { path in
            if path.status == .satisfied {
                print("We're connected! Let's grab route data")
                guard let url = URL(string: "<URL>") else { return
                    print("the JSON data didn't match")
                }
                URLSession.shared.dataTask(with: url) { (data, _, _) in //_ means we're not going to use it now
                    let routes = try? JSONDecoder().decode([Route].self, from: data!) //decoding the data
                    //allow us to interact with the app while API call is happening
                    DispatchQueue.main.async {
                        if routes != nil  {
                            completion(routes!)
//                            print(routes!)
                        } else {
                            //TODO: Update error message
                            print("we're trying to get route data - errorstate \(self.dataError), alert state \(self.showingAlert)")
                        }
                    }
                }
                .resume()
            } else {
                self.dataError = true
                print("No connection & data error set to \(self.dataError).")
            }
            print("Cell Data set to \(path.isExpensive)")
        }
        let routeQueue = DispatchQueue(label: "Route Monitor")
        routeMonitor.start(queue: routeQueue)
    }
}

Here's the call I make for onAppear to call the function

Code Block 
     //MARK: API call to get race data
      .onAppear{
        Api().getRoutes{
          (routes) in
          self.routes = routes
          print("Obserbed object: \(self.presentError.dataError)")
          if self.presentError.dataError == true {
            print("routeview error on getting data from api.getPosts \(self.presentError.dataError)")
            return
          }
        }
    }

I thought I could put an if statement after (routes) in, but I never get to that far when there is no network connecvitiy.