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There are times when you have weird Xcode build errors eg. you are absolutely sure that the referenced object is in the project, yet Xcode could not find it.

Or compile errors such as Include of non-modular header inside framework module, when you know the framework works very fine.

You can try clean (Cmd + Shift + K) and build.

But the absolute way to clean Xcode is to delete folders in ~/Library/Developer/Xcode/DerivedData. Delete the folders with your app name, and also ModuleCache.

Or simply delete all:

rm -rf ~/Library/Developer/Xcode/DerivedData/*

Purging DerivedData could well save your day.

Well, it did save me on many occasions. Here is my list of weird errors/warnings that were “solved”:

• ignoring user defined runtime attribute warning for my custom view that is IBDesignable
• Include of non-modular header inside framework module