I'm developing my first iPhone-application in Xcode and I was wondering if it is possible to get the contacts out of the Address Book of the iPhone who also use the application?
So what I need is a way to generate a unique ID based on the information in the Address Book, so that the ID that will be constructed for the same person will be the same on every iPhone where the application is used.
This way, I can use this ID as a primary key in the database I use to hold data that needs to be shared among users.
If I can construct this idea, I can also compute the ID for every Address Book member and check them against the ID's in my database to see who uses the app. But how can I construct such a unique ID?