Quick snippet to overlay Apple map data with OSM data, MapBox data, or any other map that has an online tile system on the MKMapView

Overlaying MKMapView with OSM Data

// Import these Frameworks:
#import <MapKit/MapKit.h>

// Include this delegate
@interface ViewController () <MKMapViewDelegate>


- (void)viewDidLoad
{
  // Add this code to your preexisting viewDidLoad method
  NSString *template = @"http://tile.openstreetmap.org/{z}/{x}/{y}.png";          // Tile system URL template goes here
  MKTileOverlay *overlay = [[MKTileOverlay alloc] initWithURLTemplate:template];  // Associating overlay with URL template
  overlay.canReplaceMapContent = YES;					          // Allowing overlays on MKMapView & disabling Apple map data
  [self.mapView addOverlay:overlay level:MKOverlayLevelAboveLabels];	          // Adding overlay to MKMapView above Apple lables
  self.mapView.delegate = self;                                                   // Linking the delegate to allow the next method to be called
}

 
// And this somewhere in your class that’s mapView’s delegate (most likely a view controller).
- (MKOverlayRenderer *)mapView:(MKMapView *)mapView rendererForOverlay:(id<MKOverlay>)overlay {
    if ([overlay isKindOfClass:[MKTileOverlay class]]) {
        return [[MKTileOverlayRenderer alloc] initWithTileOverlay:overlay];       // Overlay the tile with the new template
    }
    return nil;
}