FIX: Broken autocomplete / CodeSense in Xcode 4

Xcode 4 has proved somewhat in day-to-day use to be a questional improvement over Xcode 3. No other bug has reduced my productivity more than this dreaded one: all of the sudden, the autocomplete / CodeSense would stop working completely, falling back to only suggesting random, machine-parsed and cached text. 

Who knew UITableViewCells had a nil property?

Restarting, reinstalling Xcode, cleaning and rebuilding all did not work. But here’s a fix to this bug, at least until it happens again in your project.

1) Select your project from the sidebar to open project properties.

2) Select the Project and then Build Settings. Scroll down to “Build Options” to “Compiler for C/C++/Objective-C.”

Select another compiler beside the current. Build your project (ignore any errors and warnings that appear in your project.) Immediately change back to LLVM 3.0 and build. 

When you return to your code and start typing, autocomplete / CodeSense will work again!