XCode4 Transition Guide
http://developer.apple.com/library/ios/#documentation/IDEs/Conceptual/Xcode4TransitionGuide/Introduction/Introduction.html#//apple_ref/doc/uid/TP40009984-CH1-SW1

Make Connections Directly with Source Code
http://developer.apple.com/library/ios/#documentation/IDEs/Conceptual/Xcode4TransitionGuide/InterfaceBuilder/InterfaceBuilder.html#//apple_ref/doc/uid/TP40009984-CH6-SW10