Question

I’m constructing a series of MKPolygons and storing them in an array of NSValues:

for (NSDictionary* country in countries) {
    NSMutableArray* polygons = [[NSMutableArray alloc] init];

    for (NSArray* polygon in [country objectForKey:@"polygons"]) {
        CLLocationCoordinate2D polygonCoords[polygon.count];

        int i;
        for (i = 0; i < polygon.count; i++) {
            NSValue* coords = [polygon objectAtIndex:i];
            CLLocationCoordinate2D stored_coords;
            [coords getValue:&stored_coords];
            polygonCoords[i] = stored_coords;
        }

        MKPolygon* poly = [MKPolygon polygonWithCoordinates:polygonCoords count:polygon.count];
        [polygons addObject:[NSValue valueWithBytes:&poly objCType:@encode(MKPolygon)]];
        [chillPillMap addOverlay:poly];
    }
    [country setValue:polygons forKey:@"polygon_objects"];
}

However, when I try to access them later, I get two or three in and a EXC_BAD_ACCESS occurs:

for (NSDictionary* country in countries) {
   NSArray* polygon_objects = [country objectForKey:@"polygon_objects"];
   int i;
   for (i = 0; i < polygon_objects.count; i++) {
        MKPolygon* saved_poly = [MKPolygon alloc];
        [[polygon_objects objectAtIndex:i] getValue:&saved_poly];
   }
}

Not sure why this is.

Answer 1

MKPolygon is an objective-C object. You can put it into the array without converting it to a NSValue. Furthermore, you are telling NSValue to take the value of the bytes, but you are passing it the address of the pointer. Bad news.

Why not just…

[polygons addObject:poly]

then…

MKPolygon *saved_poly = [polygon_objects objectAtIndex:i];