I don't understand why the code is not executing serially. I have called the closures syncronously so that the next closure will be called only after the completion of previous one. On terminal, the last closure is printed first which I was expecting to execute in the end, then the second one & then the first one at last. Any help on this ? func getLocation(from address: String, completion: @escaping (_ location: CLLocationCoordinate2D?)-> Void) { let geocoder = CLGeocoder()   geocoder.geocodeAddressString(address) { (placemarks, error) in guard let placemarks = placemarks, let location = placemarks.first?.location?.coordinate else { completion(nil) return } completion(location) } } let queue = DispatchQueue(label: "queue") queue.sync { self.getLocation(from: self.sourceString) { location in     if(location != nil){         self.source = MKPlacemark(coordinate: location!) print("Source found") }          else{             print("Source not found") } } } queue.sync { self.getLocation(from: self.sourceString) { location in     if(location != nil){         self.destination = MKPlacemark(coordinate: location!) print("Destination found") }          else{             print("Destination not found") } } } queue.sync { if(self.source.coordinate.latitude != 0.0 && self.destination.coordinate.latitude != 0.0 ){ self.bringMap = true } else{ print("coordinates not updated yet") } }

Hi, I am new to swift and currently working on a project where I need to check if a given coordinate falls on a MKRoute or not. I searched a lot but unable to find a satisfied approach. Can someone help on this ?