I was able to get the demo project for chapter 2 of Matt&#39;s book code to successfully build.  What worked for me was to track down in xcode all of the alerts about the missing 10.5 sdk and I found that you could change the 10.5 sdk over to 10.6.  Then I got an error on build saying &quot;Path does not exist&quot;, for this I used the referenced link above, <a href="http://redwoodapp.posterous.com/macruby-and-xcode-4-build-a-self-contained-ma">http://redwoodapp.posterous.com/macruby-and-xcode-4-build-a-self-contained-ma</a>, and added the demo app target to build before the compile target.  I also changed the valid architecture to x84_64 only as mentioned in the article for good measure.