Quick one about Updates in App Store

I've got an app that works in ios3 (3.0 - 3.1.3), but they've deprecated some of the code in ios4. The problem is, if I update to the ios4 code (3.2 -) it will no longer work in the older phones.

If I release an update that is for ios4, what happens to people who have the ios3 version? Does it say "sorry you can't have it"? Does it let them overwrite it anyway and then hit them with a "upgrade to 4.0 now" box? I'm worried that they'll be offered the update, download it, overwrite the old one, and now it won't work on their old phone.*

Thanks for the help.

(*I know the upgrade to ios4 is free and all开发者_StackOverflow社区 that, but I'm pretty sure my demographic is more likely to be the "I like my phone the way it is thank you very much" type, annoyed to be forced into a new operating system just for my little app.)

I think it's your job to handle os 3 and os 4 in the same app (if you want, it's no an obligation).

You can check the OS and then do things depending on it. When you need to use a framework which only exists in OS 4, you can set a weak dependency (Target "Project Name" Info => General Tab).

By the way, you can specify your app is only for > iOS 4.0 and then user will have to update his OS before updating your app. But I never had this kind of problem. I think it's handled in the AppStore when user want to install or update an application.