We're considering hiring a contractor or intern to work with us on our iOS project but this causes me to get really paranoid that we're giving somebody who doesn't work for the company access to our precious codebase.  I mean, I could just give them access to the classes I'd like them to work on but that seems rude and it would make it more difficult for them to develop what we need them to.How paranoid should one be about people running off with their entire application?
When working with contractors/interns how protective should one be of your codebase?
freelancing;intellectual property
You should have a non compete and/or Non disclosure agreement in place when you bring them on.  This will allow you to bring in a contractor and should they choose to run off on their own and create the next Face book with out you, based on your work, you can take it all back.  But realistically that does not happen often.  If you go through a reputable company then you will probably get a professional who wants to help you succeed.  Do not hinder them by trying to compartmentalize them to the point that they want you to fail.