[Error] Could not insert new outlet connection: Could not find any information for the class named

이런 에러가 생겼을 경우

Here are some things that can fix this (in increasing order of difficulty):

• Clean the project (Product > Clean)
• Completely close Xcode and restart your project.
• Delete the Derived Data folder (Window > Projects > click Delete button by Derived Data.) (Update: In Xcode 8 this location no longer appears. Supposedly Xcode cleans up Derived Data by itself. If you want to delete it manually you can find the folder yourself by going to Preferences > Locations and clicking the gray arrow by the Derived Data folder. Then delete your project folder.)
• Click delete on the class, remove reference (not Move to Trash), and add it back again. (see this answer)