I\'m getting started on Map Kit for my job and I have a IOS project I am working on where it involves Map Kit, I know how to search for a location and pin point it but my is
Zip codes like this aren't available in MapKit. You need to find a third-party source of zip code data (e.g. codes + bounding geometries), figure out a way to index them (perhaps be using or precalculating the centroid of each), and then figure out what's close to the selected point.
Use Google Places API for this.
You can go for a Radar or NearbyPlaces search and get zip codes of the returned places (you can use a custom location and set the radius for your search as you are wishing to do).
There is a really good iOS library for querying Google Places API which is FTGooglePlacesAPI
Eventually you can also do everything manually using
NSData* data = [NSData dataWithContentsOfURL:YOUR-googleRequestURL];
and handling the fetched data.