I'm having trouble using XCode's code completion feature.
Specifically, some times it works and other times it doesn't even seem
turned on, and I can't figure out why this is. I can't seem to find
anything in the list archives to provide me with any clue, either.
Could it be because your project has not had its index updated? For me,
rebuilding the index, and possibly even doing a compile often helps
code completion out. Might explain your symptoms.