Issue with code autocompletion / syntax highlighting in Xcode 4.x

Question

I am having a rather strange issue in Xcode on one of my projects.

When I start to write my code, I am used to the auto-completion suggesting numerous entries for me

Answer 1

Most of the time I run into this problem deleting the DerivedData fixes it for me, but it one case it didn't. Turns I failed to connect the source file I created to any particular target. Once I connected it to a target source highlighting started working. If other solutions don't work, this might be your issue.