Function not returning string - swift

Question

So I'm getting back to programming and I'm having an issue. My function is not returning a value when I'm storing a Value in it. Could you guys have a look and point my out why that is happening?
func getLocation() -> NSString {
manager = OneShotLocationManager()
var tempLocation: NSString = "" // created an empty string for the var
manager!.fetchWithCompletion {location, error in
if let locatie = location {
tempLocation = String(locatie.coordinate.latitude) + "," + String(locatie.coordinate.longitude)
print(tempLocation) // It stores a value here but will not show it on the return
} else if let err = error {
tempLocation = err.localizedDescription
}
self.manager = nil
}
return tempLocation // It's not returning anything here..
}

Answer 1

The completion starts after you exit the function, so that is the problem i guess. You return "" and then do the stuff inside completion code

Answer 2

Your function is not returning the value because the fetchWithCompletion is being executed after the return statement as it is asynchronous. You can amend your function by using a completion handler to get access the tempLocation once it has been set:
func getLocation(completion: (location: String) -> ()) {
manager = OneShotLocationManager()
var tempLocation: NSString = "" // created an empty string for the var
manager!.fetchWithCompletion {location, error in
if let locatie = location {
tempLocation = String(locatie.coordinate.latitude) + "," + String(locatie.coordinate.longitude)
print(tempLocation) // It stores a value here but will not show it on the return
} else if let err = error {
tempLocation = err.localizedDescription
}
self.manager = nil
completion(location: tempLocation)
}
}
You can implement this function in the following way:
getLocation { (location) -> () in
print(location)
}

Answer 3

You need to call getLocation and do your stuff inside the fetchWithCompletion closure
func getLocation() {
manager = OneShotLocationManager()
manager!.fetchWithCompletion {location, error in
if let locatie = location {
tempLocation = String(locatie.coordinate.latitude) + "," + String(locatie.coordinate.longitude)
//DO THE THINGS YOU NEED TO DO WITH THE LOCATION HERE
} else if let err = error {
tempLocation = err.localizedDescription
}
self.manager = nil
}
}

Answer 4

The closure provided to fetchWithCompletion() is called asynchronously - upon the completion of the manager's location fetch. Your function starts the manager fetching and then returns before the manager's fetch is complete; thus the initial assignment to tempLocation is return as "".
As the fetch is asynchronous, perhaps your getLocation() should also be asynchronous?
func getLocationAsynch (handler: (String) -> Void) {
OneShotLocationManager()!.fetchWithCompletion { location, error in
if let locatie = location {
handler (String(locatie.coordinate.latitude) + "," + String(locatie.coordinate.longitude))
} else if let err = error {
handler (err.localizedDescription)
} else {
handler ("")
}
}
}
The above prevents your code from blocking; perhaps when the location becomes available you just display it for the user?
If, however, you want to block. Use a dispatch_semaphore as:
// assuming dispatch_semaphore works in Swift
func getLocation () -> String {
let sem = dispatch_semaphore_create (0);
var result = ""
OneShotLocationManager()!.fetchWithCompletion { location, error in
if let locatie = location {
result = String(locatie.coordinate.latitude) + "," + String(locatie.coordinate.longitude)
} else if let err = error {
result = err.localizedDescription
}
dispatch_semaphore_signal(sem)
}
dispatch_semaphore_wait(sem)
return result
}