CODEWITHSUNDEEP
objective-cswiftmkmapviewmkpolygon
gotnull
gotnull

Reputation: 27214

Converting MKPolygon Objective-C code to Swift

I have the following Objective-C method:

- (void)addPolygonToMap {
    NSInteger numberOfPoints = [self.coordinates count];
    
    if (numberOfPoints > 4) {
        CLLocationCoordinate2D points[numberOfPoints];
        for (NSInteger i = 0; i < numberOfPoints; i++) {
            points[i] = [self.coordinates[i] MKCoordinateValue];
        }
        
        self.polygon = [MKPolygon polygonWithCoordinates:points count:numberOfPoints];
        [self.mapView addOverlay: self.polygon];
    }
    
    self.isDrawingPolygon = NO;
    [self.drawPolygonButton setTitle:@"draw" forState:UIControlStateNormal];
    self.canvasView.image = nil;
    [self.canvasView removeFromSuperview];
}

My attempt at converting it to Swift:

func addPolygonToMap() {
    var numberOfPoints: NSInteger = self.coordinates.count
    
    if (numberOfPoints > 4) {
        var points: [CLLocationCoordinate2D] = []
        var coordsPointer = UnsafeMutablePointer<CLLocationCoordinate2D>.alloc(numberOfPoints)

        for i in 0..<numberOfPoints {
            points.append(coordsPointer[i])
        }
        
        self.polygon = MKPolygon(coordinates: &points, count: numberOfPoints)
        self.mapView.addOverlay(self.polygon)
        
        coordsPointer.dealloc(numberOfPoints)
    }
    
    self.isDrawingPolygon = false
    self.drawPolygonButton.setTitle("Draw", forState: .Normal)
    self.canvasView.image = nil
    self.canvasView.removeFromSuperview()
}

Finally, when the delegate method is called it's not actually adding the overlay to the mapView. I can't see anything.

I'm assuming it's my self.addPolytonToMap() method, but I'm not 100% sure. The whole scenario works fine in my Objective-C project.

func mapView(mapView: MKMapView!, rendererForOverlay overlay: MKOverlay!) -> MKOverlayRenderer! {
    if (overlay is MKPolygon) {
        var overlayPathView = MKPolygonRenderer(overlay: overlay)
        overlayPathView.fillColor = UIColor.cyanColor().colorWithAlphaComponent(0.2)
        overlayPathView.strokeColor = UIColor.cyanColor().colorWithAlphaComponent(0.2)
        overlayPathView.lineWidth = 5
        
        return overlayPathView
    } else if (overlay is MKPolyline) {
        var overlayPathView = MKPolylineRenderer(overlay: overlay)
        overlayPathView.strokeColor = UIColor.blueColor().colorWithAlphaComponent(0.7)
        overlayPathView.lineWidth = 5
        
        return overlayPathView
    }
    
    return nil
}

UPDATE:

I just noticed that in my Objective-C version, the points[i].latitude are coming through okay, however when I do the following I get a strange output:

println(coordsPointer[i].latitude)

Output:

1.63041663127611e-321

1.64523860065135e-321

1.65511991356818e-321

1.68970450877706e-321

1.7045264781523e-321

1.72922976044436e-321

This would explain why I don't see the overlay, however my experience with UnsafeMutablePointer<> is limited.

Upvotes: 1

Views: 1319

Answers (1)

gotnull
gotnull

Reputation: 27214

Fixed by modifying the addPolygonToMap() method:

func addPolygonToMap() {
    var numberOfPoints: NSInteger = self.coordinates.count

    if (numberOfPoints > 4) {
        var points: [CLLocationCoordinate2D] = []

        for i in 0..<numberOfPoints {
            points.insert(self.coordinates[i].MKCoordinateValue, atIndex: i)
        }

        self.polygon = MKPolygon(coordinates: &points, count: numberOfPoints)
        self.mapView.addOverlay(self.polygon)
    }

    self.isDrawingPolygon = false
    self.drawPolygonButton.setTitle("Draw", forState: .Normal)
    self.canvasView.image = nil
    self.canvasView.removeFromSuperview()
}

Thanks to @Volker for the help.

Upvotes: 3

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