4.3 app won't work on 3G iPhone running iOS 4.2.1?

Question

I'm fairly new to this so please go easy on me if this is a dumb question. I set the base SDK to 4.3 and deployment target to 4.0 so in theory, it should run on everything in-between. The app works with no problems on all iPad and iPhone simulator versions between 4.0 to 4.3. However, when I uploaded the .ipa file to testflightapp.com and someone tested it on an iPhone 3G running OS 4.2.1, it seems to crash on launch. Since it runs fine on the same version of the simulator, this makes me think there is something in project settings I haven't done right. I've looked through the 4.3 upgrade notes and I'm not making use of any of the added features so that doesn't seem to be my problem. Setting the base SDK and deployment target were the only things I've done in terms of customizing the project for different iOS versions. Is there anything else I could try to make it run on that iPhone?

Answer 1

I figured out what it was (forgot to come back to my question). I was running into the watchdog which closes apps if a few doesn't appear 20 seconds after launching. Since it was an iPhone 3G with iOS4 and a bunch of stuff running in the background, the guy was basically using the slowest device possible.

Answer 2

Most probably you're using API methods that doesn't exist in 4.2.1 yet. So when you try to run them there, the application crashes. If you ask your tester to check their log, you might get an idea of what could be the problem.

EDIT: Urgh, sorry, I just saw that it runs fine in the simulator. Can you get the crash message to give us more hints about it?

Answer 3

Make sure all devices that you are trying to run the App on are listed in the iOS Provisioning Portal. Check your certificates and provisioning profiles in xCode and your keychain with the iOS Help Documents to ensure that you have built the App with all the necessary dev requirements.

Also, Enable 'Developer Logging' on the device (in the Settings App) and import the logs into xCode via the 'Devices' tab in xCode's 'Organizer'.

If your target iOS version is 4.0, then it should run on anything from 4.0+ even if the base SDK is 4.3. Xcode will warn you if you use a class/method/feature that is not available for the target version (assuming you have live issues enabled in xcode).