Publishing iPhone app that supports iOS 3.1 plus

Question

We are about to issue version 4.0 of our iPhone app and have had some complaints recently that previous versions are only available from iOS 4.1 plus. I know that to change this I can set my Deployment Target (In Project>Build) to iOS 3.1. However, I've run through the app on an emulator and again on my iPhone (uses iOS 4.2) but I'm not able to test on anything older as everyone here has the same iOS or 4.3. Can I safely assume that just by changing the Deployment Target and testing the app on later models that the app will run safely on later versions like 3.1.

We are familiar with the reason why people with older iPhones wont upgrade to iOS 4.0 and above, so we would like to accomodate them but not if it means the app is unsound and we have no way of testing it.

Answer 1

No, just because it compiles and runs on newer version of the SDK does not mean that it will work on older versions. If you're using features that are only available in iOS 4+ you'll need to check for their existence before using them; your app will crash otherwise.

There are some subtleties that you'll probably miss the first time too (or at least I did). In short, there's no real alternative to testing.

Answer 2

for the problem you have you need to install older versions of xcode having ios 3.0 support and you need to check whether it's working on the same or not as there are lots many changes in os 4.0 and above so it's definite that the application will not work with the ios 3.0, 3.1 available device and it will crashed.

Just install older version of SDK and test on simulator , if works then fine else you need to make code according to ios version 3.0 and ios version 4.0 in your code by differentiating the os and run the code accordingly.