Jun 22, 2011
Restoring CodeSense in Xcode 4
Maybe this can help. If you are using Xcode 4, you noticed that the Rebuild Index of Xcode 3.x disappeared.
For some reasons, the code completion of Xcode did not work today. To restore its functionality, open the Organizer, select the Projects tab and on the left hand side, select the project that gives you the problem. To fix it, just press the Delete... button corresponding to the Derived Data.