Possible Duplicate:
Install xCode 3.2.3 w/ iPhone SDK 4, get “Base SDK missing”, can't see other SDKs
I just upgraded my xcode directly from the website i.e. I downloaded the new version of xcode which came with ios4 – yet when I finished installing everything including the SDK it now says base sdk missing?!?
you have du update your app, too.
in
Groups & Filesklick onTargetsand doubleclick you application.then select your configuration and search for
Base SDKunder theArchitecturessection. select the 4.0 there