When XCode 4’s Code Completion (autocomplete) Breaks

Here’s how to fix it:

1. Close the project, leaving XCode still running.
2. Open XCode’s Organizer window, go to the Projects Tab, select the correct project, and hit the Delete button next to “Derived Data”.
3. Quit XCode.
4. Navigate to your project’s .xcodeproject file in Finder.  Right-click, choose “Show Package Contents.”
5. Leave the project.pbxproj file, but delete the project.xcworkspace file, any .pbxuser files, and the entire userdata folder.
6. Open the project in XCode.  You will see XCode riding high on the CPU usage for around 10-60 seconds, depending on the size of your project.  The activity window will say “Indexing”
7. When your CPU spike returns to earth, code completion will be working again.

Unlike rebuilding the indexes alone, this procedure works every time.  It’s unfortunate that XCode’s indexes are brittle enough to break once a week, but now you know how to fix it!

Is code completion working for system libraries and your own code, but not for one particular third-party library?

Make sure that if you’re using

#include "something.h"

syntax, the path to the .h files is in “User Header Search Paths” (not Header Search Paths).

Make sure that if you’re using

#include <something.h>

, the path to the .h files is in “Header Search Paths” (not User Header Search Paths).

When you build your project, the compiler appears to give you grace if you’ve accidentally put the header files into the wrong type of search path, but code completion is less forgiving.

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