There isn’t really an autoformat option in Xcode.
There is an option ^I (Control-I) to re-indent the code, which will re-align the code according to the tab width set in your preferences, but that’s about as far as it goes.
You might have better luck with a text editor like TextMate? I don’t know for certain, but I know it supports Objective-C and has some macros, there may be a reformat option?