Xcode 6.3 shows random files instead of counterparts in assistant editor

Question

I always have my Xcode assistant editor open with counterparts option. It's very handy to have an *.m file opened at standard editor while having corresponding *.h file in assistant editor.

After recent update to version 6.3 Xcode started to show random instead of corresponding headers quite often. Several clicks to "four squares" icon and mode usually brings it back (but it's very annoying).

Do you experience this too? How to fix it?

Note: deleting DerivedData didn't helped

Answer 1

As a workaround, one could use the Reset Editor command with the keyboard shortcut Command+Option+Shift+Z (US keyboard layout). If your keyboard layout doesn't match, you can see the key binding in View->Assistant Editor->Reset Editor. A word of caution, though, this will close any additional Assistant Editors you may have opened (the ones that open by clicking "+").

Another thing I noticed is the bug happens when you are switching Xcode windows or tabs but not when you are switching files within the same tab.

Answer 2

It looks like it's a just bug after all. I filed a bug report rdar://20684654. For a workaround see the accepted answer.

UPDATE: it's fixed in Xcode 6.4 beta