Question

I’m about to develop my first iOS application and as far as OS support goes, should I be building against iOS 6 or iOS 5? What’s the typical industry practice when a new iOS is about to be released? Also, how is the backwards compatibility? By that I mean, if I were to build for 5, will users running 6 also be able to install and run it when they download it from the App Store? Also, what are the typical statistics of upgrade v.s. not upgrade when it comes to new iOS releases for iPhone and iPad users. Any blogs/references or personal experiences regarding this topic would be great!

Answer 1

You will probably quickly develop using the iOS6 SDK.

But using the iOS6 SDK don’t mean that your app will only be compatible with iOS6. It only means that you will be able to use all methods that exists in iOS6, including methods that already existed in previous APIs (in iOS5 for example), and new APIs introduced in iOS6.

So even if you use the iOS6 SDK, your application will be compatible with iOS5 and iOS6 as long as you use methods that were already present in iOS5 (the majority of them).

• If you use methods that were already present in iOS5 and are still present in iOS6 (that is the majority of the methods of the SDK), your application will work in both iOS5 and iOS6. But you won’t take advantage of the new stuff introduced in iOS6 that were not present in iOS5, as iOS5 users won’t have these features in their OS.
• You can use new methods introduced in iOS6 and that were not present in iOS5, but then either you drop the iOS5 support, or you have to make sure to check the method availability before using it. For example, if you intend to have a button that makes use of some classes or methods that only have been introduced in iOS6 and were not present in iOS5, check the availability of the class or method first, and only call it if it is available. And you may inform the user that this feature is unavailable for him if the class/method is not available in his version of the OS, encouraging him to upgrade its OS version.

For more info, I strongly recommend you read the SDK Compatibility Guide from Apple documentation, that explains it all: the difference between the version of the SDK and the version of the OS you support, how to make checks to see if a method newly introduced in the latest SDK can be used (namely prevent to use an method that was inexistant in iOS5 if the user is running iOS5), and so on.