Here’s a library that allows you to very easily show directions within many popular map apps called CMMapLauncher from Citymapper.

CMMapLauncher provides a simple syntax for detecting whether a directions app is installed, and setting up those directions.

Here’s an example from the readme showing how to detect if the Citymapper app is installed:

BOOL installed = [CMMapLauncher isMapAppInstalled:CMMapAppCitymapper];

and an example showing how to launch directions within the Citymapper app:

CLLocationCoordinate2D bigBen = CLLocationCoordinate2DMake(51.500755, -0.124626);
[CMMapLauncher launchMapApp:CMMapAppCitymapper
            forDirectionsTo:[CMMapPoint mapPointWithName:@"Big Ben"
                                              coordinate:bigBen]];

The apps supported by CMMapLauncher include: Apple Maps, Google Maps, Citymapper, Navigon, The Transit App, Waze and Yandex Navigator.

You can find CMMapLauncher on Github here.