Using Xcode 7.3
, sometimes randomly the editor turns to be black, no syntax colours , but worse- no auto complete for local variables and functions.
When you compile again, you get the colours back , but still no auto complete. Sometimes there is a message that there is a problem with the editor.
I did not have this problem before (5 years), and I'v read this thread which does not seems like the same problem, because its too old : Xcode: code loses syntax coloring
This might seems like a small thing, but without the auto-complete -its really hell !