Xcode 7.3 autocomplete is so frustrating

Question

There is a new autocomplete in Xcode. Probably might be useful because it checks not only beginning of names etc. But I found that very often it doesn\'t find a class name o

Answer 1

just open Xcode derived data folder and delete the folder

/Users/yourUserName/Library/Developer/Xcode/DerivedData

then restart Xcode, now autocompletion works like a charm