This error is probably due to the fact that you didn't implement one of more languages you chose to localize in your application settings.
In order to implement a language in a storyboard :
- Select the storyboard
- On the right panel, go to the File inspector tab (first from the left)
- In Localization, check all language(s)
You now have two ways to localize your storyboard :
- Either you choose to create a
.strings
file for your language by choosing Localizable Strings, this will generate a list of strings xcode found in your storyboard. - Or you can choose to create a "sub"-storyboard by choosing Interface Builder Cocoa Touch Storyboard which creates a different version of your storyboard for a particular language.
So far I only found one way to refresh the .strings file in xcode if you add new strings : simply uncheck and recheck the language and select "Replace File" when asked. Apple also provides a tool you can use in the terminal. Finally there's a script that does it automatically.