问题
I build my project with the latest SDK (4.1) and set "iOS Deployment Target" (3.0). Can I run my project on a real iPhone 3.0 if I use some methods of 4.0 sdk?
回答1:
You can only run your project on OS 3 devices if you conditionally code around the OS 4 methods you want to use. If you called a method that only existed in iOS 4 on an iOS 3 device your app would crash. You can do this through both checking iOS version numbers and using the [... respondsToSelector:] method.
来源：https://stackoverflow.com/questions/4700013/sdk-and-ios-deployment-target