I am having an extremely frustrating issue with XCode 7.3 (however, this issue has persisted since I installed XCode 7.2) and Swift code, and I am hoping others have had this issue and know how to resolve it. Syntax highlighting and code completion work perfectly fine in Objective-C files, and also works fine when calling other Swift objects within Swift code. However, any Objective-C objects or methods mentioned in Swift code get no syntax highlighting, and XCode will not complete ANY Objective-C declared methods or properties. Everything compiles and runs just fine.
I should also add that I have also tried doing a completely clean install of XCode. I deleted all my derived data, deleted all XCode caches, and deleted my XCode preferences files (in addition to obviously deleting the XCode.app archive before re-installing).
It is making it extremely difficult to develop in Swift. I don't want to do this, but if I can't find a way to resolve this I'll be forced to go back to using Objective-C.
I have the same problem. But finally solved it. I make two change, not sure which is the key point but you can try them all.
Within the same folder as your project's Derived Data is a Module Cache. When Code Completion stopped working, deleting this fixed it.
Close Xcode and delete the ~/Library/Developer/Xcode/DerivedData/ModuleCache directory.
Go to the Build Settings of your target, then search Enable Modules
If it's Yes, change it to No, and you may get some build error, just change it back to Yes.
After two steps above you should Clean(Shift+Command+K) your project.
For now you may fixed the problem.