How to Call Background Fetch Completion Handler Properly - ios

Question

Currently, I am using an API (PowerAPI) in which the "authenticate" function is called and then once the user's data has been processed, a notification is sent out. This authenticate function needs to be called as a background fetch. My question is whether my current way of calling the completion handler is even calling the completion handler and if there is a better way?
Currently this is in my app delegate class:
let api = PowerAPI.sharedInstance
var completionHandler: ((UIBackgroundFetchResult) -> Void)? = nil
func application(application: UIApplication, performFetchWithCompletionHandler completionHandler: (UIBackgroundFetchResult) -> Void) {
print("BG fetch start")
NSNotificationCenter.defaultCenter().addObserver(self, selector: "handleTranscript:", name:"transcript_parsed", object: nil)
self.completionHandler = completionHandler
api.authenticate("server.com", username: "User", password: "password", fetchTranscript: true)
}
func handleTranscript(notification : NSNotification){
print("BG fetch finit")
completionHandler!(UIBackgroundFetchResult.NewData)
print(api.studentInformation)
}
The API is a singleton type object.
EDIT: The PowerAPI object is a class I wrote to download student data from a server and parse it. The "transcript_parsed" notification is a notification generated from within the PowerAPI directly after the "transcript_fetched" notification is sent out in the following asynchronous code (Also within PowerAPI):
let task = session.dataTaskWithRequest(request) {
(let data, let response, let error) in
guard let _:NSData = data, let _:NSURLResponse = response where error == nil else {
print("error")
return
}
switch notificationID {
case "authentication_finished":
//NSString(data: data!, encoding: NSUTF8StringEncoding)! //used to return data from authentication
let success = self.parse(data!) //notification object is true if success
NSNotificationCenter.defaultCenter().postNotificationName(notificationID, object: success)
case "transcript_fetched":
NSNotificationCenter.defaultCenter().postNotificationName(notificationID, object: data)
default:
break
}
}