http://www.cnblogs.com/yjmyzz/archive/2011/01/25/1944325.html
下面这个事苹果官方的
https://developer.apple.com/library/mac/documentation/IDEs/Conceptual/xcode_help-command_shortcuts/MenuCommands/MenuCommands014.html#//apple_ref/doc/uid/TP40010560-CH2-SW1