ios - GCD Semaphore does not wait (Swift) -

i'm pretty new gcd. have function forward geocoding , issue returns before completion closure completes. every time returns nil. found out can use semaphores return waits completion closure complete, there little examples online , found none of function returns. tried implement it, function still returns nil though location printed out console moments later. if tell me making mistake grateful.

func forwardgeocoding(address: string) -> cllocation? {     var userlocation: cllocation?     var returnvalue: cllocation?     let semaphore = dispatch_semaphore_create(0)      clgeocoder().geocodeaddressstring(address, completionhandler: { (placemarks, error) in         if error != nil {             print("geocoding error: \(error)")             return         }         if placemarks?.count > 0 {             let placemark = placemarks?.first             let location = placemark?.location             let coordinate = location?.coordinate             print("settings location: \(coordinate!.latitude), \(coordinate!.longitude)")             if let unwrappedcoordinate = coordinate {                 let clreadylocation: cllocation = cllocation(latitude: unwrappedcoordinate.latitude, longitude: unwrappedcoordinate.longitude)                 userlocation = clreadylocation                 dispatch_semaphore_signal(semaphore)             }         }     })      let wait = dispatch_semaphore_wait(semaphore, dispatch_time_forever)      if wait != 0 {         returnvalue = userlocation     }     return returnvalue } 

as paulw11 mentioned, semaphore in case bad programming habit. if new gcd learn understand asynchronous pattern returning received data in completion block. it's simpler handle in swift in objective-c.

this example using completion block:

func forwardgeocoding(address: string, completion: (cllocation?, nserror?) -> void) {    clgeocoder().geocodeaddressstring(address, completionhandler: { (placemarks, error) in     if error != nil {        completion(nil, error!)     } else {       if let placemarks = placemarks !placemarks.isempty {         let placemark = placemarks.first!         if let unwrappedlocation = placemark.location {           let coordinate = unwrappedlocation.coordinate           print("settings location: \(coordinate.latitude), \(coordinate.longitude)")           let clreadylocation = cllocation(latitude: coordinate.latitude, longitude: coordinate.longitude)           completion(clreadylocation, nil)         }       }     }   }) } 

and call with

forwardgeocoding("foo") { (location, error) in   if error != nil {     print("geocoding error: \(error!)")   } else {     // location   } }