CLGeocoder().reverseGeocodeLocation; what is the handler supposed to be?

This is the code I am using. I am unsure of what variables should be passed into the completion handler. Every other post I view says to pass 'placemark' and 'error' but I am running into warnings and errors.

func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
    CLGeocoder().reverseGeocodeLocation(manager.location!, completionHandler:{ ([placemark: CLPlacemark?], error: NSError?) in
        print(error)
    })
}

Here is the complete function:

func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation]){

    CLGeocoder().reverseGeocodeLocation(manager.location!, completionHandler: {(placemarks, error)-> Void in

        currentLatitude = String(manager.location!.coordinate.latitude)
        currentLongitude = String(manager.location!.coordinate.longitude)

    })
}

Hope this helps!