This is more of a regression or rather a feature request for OS X / Xcode. In 4.7 the engine source was part of the Xcode project, but it is no longer part of projects generated in 4.8. Having the engine source as part of the Xcode project was very convenient because you could just command + click on any of the engine provided class methods/functions and jump directly to their definition and read actual source code and how they are implemented.
Having that is huge, at least for me, when developing and learning the engine in general.
Having the engine sources as part of the Xcode project files might be scary to people, but they can be part of the project file and not associated to any compile target and as such they’ll never compile, or, worse case, associated to some dummy target.
My current solution is to manually add the engine source to the Xcode project, but it would be nice if that was done by default, especially since "it used to work"™