Apple has released the second preview of Xcode 4 to developers for both Mac and iOS development.
The release requires Mac OS X 10.6 Snow Leopard, and includes the iOS SDK 4, to develop apps for Mac, iPhone, and iPad.
What's New: Xcode 4 has a brand new, single window interface for all major workflows Interface Builder is now integrated within the main Xcode IDE Assistant shows a paired editor with complementary files (headers, UI controllers, etc.) Fix-it highlights code where an error is detected. as you type, and can even fix it for you Version editor shows a live comparison through SCM history, using Git or Subversion LLVM compiler 2.0 includes full support for C, Objective-C, and now C++ LLDB debugger is faster, and uses less memory than the GDB debugging engine - see notes below on how to enable the LLVM compiler or LLDB debugger Instruments adds System Trace, and new iOS instruments including OpenGL ES