As far as I know there is no official way to create Xcode 4 plugins (just like there wasn’t one for v3.x).
Here is an openradar on Xcode’s lack of plugin support:
Please support the ability for 3rd
parties to extend Xcode via a public
plugin API. Aperture, Visual Studio,
Eclipse, TextMate and other
applications benefit from this
ability. I would like to see more
advanced refactorings, code analysis
(think Resharper by Jetbrains) and
Provide plugin API for Xcode 4 (rdar://8622025)
Please dupe this if you want plugins!
Edit: Just stumbled upon this:
“Xcode 4 does support user-defined
plugins, see CLITool-InfoPlist
for an example of a working Xcode 4
plugin. You just have to add
XC4Compatible (true) in the
That being said these GitHub repos might be handy, too:
Xcode4 Plugin-API Documentation (link dead)
Xcode Plugin Template (link updated)
Further more mogenerator‘s Xmod plugin might be a good starting point.
(Wasn’t Xcode-4 compatible yet, last time I checked, though)