在reverseGeocodeLocation（Swift2）中更改变量值

Question

我在更改字符串变量值时遇到问题，代码看起来像这样

self.mapView是一个MKMapView

代码的作用：它抓住手指触摸点并在其中放置注释，并使用CLGeocoder（）。reverseGeocodeLocation我想抓住此人的地址，但是当我尝试将地址存储在变量中时，它只会直接返回nil在CLGeocoder（）。reverseGeocodeLocation中使用注释 。标题确实会改变其值在这里有什么用？

func longPressAction(gestureRecognizer: UIGestureRecognizer) {

        if (gestureRecognizer.state == UIGestureRecognizerState.Began) {
            let touchPoint = gestureRecognizer.locationInView(self.mapView);
            let annotation = MKPointAnnotation();
            let newCoords = self.mapView.convertPoint(touchPoint, toCoordinateFromView: self.mapView);
            let location = CLLocation(latitude: newCoords.latitude, longitude: newCoords.longitude);
            var address:String = ""; // Doesn't store here!
            CLGeocoder().reverseGeocodeLocation(location) { (placemarks, error) -> Void in
                if (error != nil) {
                } else {
                    if let p = placemarks?[0] {

                        if (p.subThoroughfare != nil) {
                            address = p.subThoroughfare!;
                        } else if (p.subThoroughfare == nil && p.thoroughfare != nil) {
                            address = p.thoroughfare!;
                        } else if (p.subThoroughfare == nil && p.thoroughfare == nil && p.country != nil) {
                            address = p.country!;
                        } else if (p.subThoroughfare == nil && p.thoroughfare == nil && p.country == nil) {
                            address = "New Place";
                        }
                    }
                }
            }
            print(address)
            annotation.title = address;
            annotation.coordinate = newCoords;
            self.mapView.addAnnotation(annotation);
            sharedAnnotations.addObject(annotation);
    }

打印输出（地址） 为零

Answer 1

我给你看我的榜样

   func returnPlaceMark(coordinate: CLLocationCoordinate2D, completaion: (superPlace: MKPlacemark) -> ()) {
        let geocoder = CLGeocoder()
        let location = CLLocation(latitude: coordinate.latitude, longitude: coordinate.longitude)

        geocoder.reverseGeocodeLocation(location) { (arrayPlaceMark, error) -> Void in
            if error == nil {
                let firstPlacemark = arrayPlaceMark!.first!
                completaion(superPlace: MKPlacemark(placemark: firstPlacemark))
            }
        }

Answer 2

发生这种情况是因为您要在块内设置address 。 完成获取反向位置后， CLGeocoder().reverseGeocodeLocation异步调用此块。 这就是为什么当您尝试立即在函数中打印它时，它是空的。 如果将其打印在块内，则会看到其具有正确的值。

您的函数可能如下所示：

func longPressAction(gestureRecognizer: UIGestureRecognizer) {

    if (gestureRecognizer.state == UIGestureRecognizerState.Began) {
        let touchPoint = gestureRecognizer.locationInView(self.mapView)
        let annotation = MKPointAnnotation()
        let newCoords = self.mapView.convertPoint(touchPoint, toCoordinateFromView: self.mapView)
        let location = CLLocation(latitude: newCoords.latitude, longitude: newCoords.longitude)

        CLGeocoder().reverseGeocodeLocation(location) { [weak self] (placemarks, error) -> Void in
            if let strongSelf = self{
                if (error != nil) {
                } else {
                    if let p = placemarks?[0] {
                        var address:String = ""

                        if (p.subThoroughfare != nil) {
                            address = p.subThoroughfare!
                        } else if (p.subThoroughfare == nil && p.thoroughfare != nil) {
                            address = p.thoroughfare!
                        } else if (p.subThoroughfare == nil && p.thoroughfare == nil && p.country != nil) {
                            address = p.country!
                        } else if (p.subThoroughfare == nil && p.thoroughfare == nil && p.country == nil) {
                            address = "New Place"
                        }

                        print(address)
                        annotation.title = address
                        annotation.coordinate = newCoords
                        strongSelf.mapView.addAnnotation(annotation)
                        strongSelf.sharedAnnotations.addObject(annotation)
                    }
                }
            }
        }
    }