For building iOS apps you need a Mac. That seemed to be a challenge in itself. But integrating the system into our Windows domain, logging in with Active Directory accounts, accessing file servers, etc. was surprisingly easy. Apple did a good job in Mac OS X supporting Windows environments. Next step was to get accustomed to a new development environment. Apple’s is called Xcode. It comes with an iPhone simulator for running and debugging your app on the Mac itself. Everybody puts his pants one leg at a time, so writing, compiling and debugging software is not that different in general. But getting your app onto an actual iOS device is a somewhat complicated process.

As an Apple software developer you need to participate in the Apple iOS developer program. After you sign up on the Apple website you need a code signing certificate, which is a private/public key pair you use for digitally signing your executables. Getting one involves creating a certificate signing request file on the mac,  uploading it to the Apple developer website and downloading your Apple- signed certificate. When you build your app, Xcode digitally signs it using the private part of your certificate. Unsigned Apps  won’t run on any iOS device.

When you use an iPhone connected to your Mac for development, Xcode generates a “provisioning profile”. That’s a file containing the public part of your developer certificate and the unique device ID (UDID) of your iPhone. The profile is digitally signed by Apple. Now when you’re installing your app, iPhone checks the provisioning profile. If it’s correctly signed by Apple, contains the public key matching the private one you’re using to sign your app and if the profile’s UDID matches the phone, your app will install  and run. Fortunately Xcode hides most of signing and provisioning details from you, which get’s you started rather easily.

On the other hand it prevents you from really understanding the app signing and distribution process which you need to master in order to get your app on QA- or beta testers devices or later distributed to customers. But that’s another story, I’ll tell you another time on this blog.