iPhone App baseSDK and iOS deployment target

I am in the process of deploying my app to the app store. I am not sure what to set for baseSDK and iOS depl开发者_开发技巧oyment target. I have the latest iOS 4.1 installed. How can I make sure that it runs on all the devices. My application was build on 4.0.1 (I think).

My iPod has iOS 4.1 (latest) and my iPhone has 4.0. To make my application work on the iPhone I have to lower the baseSDK and iOS deployment target to 3.2.

You generally want to build against the latest SDK, but set the deployment target to the earliest you can. So, to run on as many devices as possible, use SDK 4.1, but set your deployment target to 3.0 or 3.1.3. I strongly suggest getting hold of an older iPod touch and testing on older devices if you want to support them. Its easy to miss an API call that's only supported on, say, 4.0.