块执行后如何返回值？迅速

Question

我想从函数中获取价值。功能上有一个障碍。当块执行时，该功能已返回该值。我尝试了许多不同的方法，但它们并没有帮助我。我用NSOperation和调度。该函数始终返回值，直到执行块为止。

   var superPlace: MKPlacemark!

 func returnPlaceMarkInfo(coordinate: CLLocationCoordinate2D) -> MKPlacemark? {
    let location = CLLocation(latitude: coordinate.latitude, longitude: coordinate.longitude)
    geocoder.reverseGeocodeLocation(location) { (arrayPlaceMark, error) -> Void in
            if error == nil {
                let firstPlace = arrayPlaceMark!.first!
                let addressDictionaryPass = firstPlace.addressDictionary as! [String : AnyObject]

                self.superPlace = MKPlacemark(coordinate: location.coordinate, addressDictionary: addressDictionaryPass)
            }
        }

    return superPlace
}

Answer 1

您不能简单地返回此处，因为reverseGeocodeLocation函数正在异步运行，因此您将需要使用自己的完成块：

var superPlace: MKPlacemark!

func getPlaceMarkInfo(coordinate: CLLocationCoordinate2D, completion: (superPlace: MKPlacemark?) -> ()) {
    let location = CLLocation(latitude: coordinate.latitude, longitude: coordinate.longitude)
    geocoder.reverseGeocodeLocation(location) { (arrayPlaceMark, error) -> Void in
        if error == nil {
            let firstPlace = arrayPlaceMark!.first!
            let addressDictionaryPass = firstPlace.addressDictionary as! [String : AnyObject]

            self.superPlace = MKPlacemark(coordinate: location.coordinate, addressDictionary: addressDictionaryPass)
            completion(superPlace: superPlace)
        } else {
            completion(superPlace: nil)
        }
    } 
}