How to get directions to a MKPointAnnotation

I have created a map that has an MKPointAnnotation which is the single point on the map (besides the users location). I am trying to work out how to amend some existing code I have to get the Driving directions to this point.

This is the code that I use early in the application. At this earlier point in the application I have the following which gives me a CLPlaceMark.

[geocoder geocodeAddressString:location
             completionHandler:^(NSArray* placemarks, NSError* error){
                 if (placemarks && placemarks.count > 0) {
                     CLPlacemark *topResult = [placemarks objectAtIndex:0];

Collecting directions:

MKDirectionsRequest *request = [[MKDirectionsRequest alloc] init];
                         [request setSource:[MKMapItem mapItemForCurrentLocation]];
                         MKPlacemark *mkDest = [[MKPlacemark alloc] initWithPlacemark:topResult];
                         [request setDestination:[[MKMapItem alloc] initWithPlacemark:mkDest]];
                         [request setTransportType:MKDirectionsTransportTypeWalking]; // This can be limited to automobile and walking directions.
                         [request setRequestsAlternateRoutes:NO]; 
                         MKDirections *directions = [[MKDirections alloc] initWithRequest:request];
                         [directions calculateDirectionsWithCompletionHandler:^(MKDirectionsResponse *response, NSError *error) {
                             if (!error) {
                                 for (MKRoute *route in [response routes]) {
                                     [self.mapView addOverlay:[route polyline] level:MKOverlayLevelAboveRoads]; // Draws the route above roads, but below labels.
                                     // You can also get turn-by-turn steps, distance, advisory notices, ETA, etc by accessing various route properties.
                                 }
                             }
                         }];

Issue
The issue is that later on I seem to only be able to access the self.mapView.annotations. So I have access to the MKPointAnnotation, but I need access to a CLPlacemark for the setDestination on the MKDirectionsRequest.

So the question is how do I get a CLPacemark from a MKPointAnnotation, or is there a different approach to getting directions to a single point without that requirement? Thanks

For the directions request, the MKMapItem needs an MKPlacemark (not a CLPlacemark).

You can create an MKPlacemark directly from coordinates using its initWithCoordinate:addressDictionary: method.

For example:

MKPlacemark *mkDest = [[MKPlacemark alloc] 
                          initWithCoordinate:pointAnnotation.coordinate 
                           addressDictionary:nil];

[request setDestination:[[MKMapItem alloc] initWithPlacemark:mkDest]];