I recently ran into this issue with a large mostly-objc project. Hopefully this helps somebody.
For me autocomplete had been working before in this project but then began to fail for all objective c classes / methods. The project still compiled with no issues though.
I ended up commenting out all of the existing imports in the bridging header and adding a simple test class, for which auto complete worked. Then uncommenting each of the other imports until I isolated which one caused the problem.
For example my header basically looked like this:
#import "MyClass.h" #import "MyOtherClass.h" #import "SomeThirdPartyModule.h" etc...
I did this:
#import "SimpleTestClassWithOneMethod.h" // #import "MyClass.h" // #import "MyOtherClass.h" // #import "SomeThirdPartyModule.h"
And autocomplete started working for SimpleTestClass when used from Swift.
Then started uncommenting other classes from the bridging header until it worked. The import that caused the problem was some third party framework, not sure why it caused an issue but I just pulled out what I needed from that particular header for my swift code and imported it separately.