Objective-C category to get the radius of an MKMapView

MKMapView+Utilities.m

//
// Created by Joel Drotleff on 11/19/13.
// Copyright (c) 2013 Joel Drotleff. All rights reserved.
//


#import <MapKit/MapKit.h>
#import <CoreLocation/CoreLocation.h>
#import "MKMapView+Utilities.h"


@implementation MKMapView (Utilities)

- (CLLocationDistance)getRadius
{
    // init center location from center coordinate
    CLLocation *centerLocation = [[CLLocation alloc] initWithLatitude:self.centerCoordinate.latitude
                                                            longitude:self.centerCoordinate.longitude];
    double topCenterLat = centerLocation.coordinate.latitude-self.region.span.latitudeDelta/2.;
    CLLocation *topCenterLocation = [[CLLocation alloc] initWithLatitude:topCenterLat
                                                             longitude:centerLocation.coordinate.longitude];

    CLLocationDistance distance = [centerLocation distanceFromLocation:topCenterLocation];
    return distance;
}

@end