Looking at the screencast I was surprised to see this macro syntax being allowed (passing an asterisk here means all properties get synced):

  NSRailsSync(*)

Here's what's happening. Ingenious stuff.

  //adding a # before va_args will simply make its contents a cstring
  #define _MAKE_STR(...)	NSRStringFromCString(#__VA_ARGS__)

  //define NSRailsSync to create a method called NSRailsSync, which returns the entire param list
  #define NSRailsSync(...) \
  + (NSString*) NSRailsSync { return _MAKE_STR(__VA_ARGS__); }