Swift : How to change language inside app?

found my answer :

NSUserDefaults.standardUserDefaults().setObject(["language identifier"], forKey: "AppleLanguages") 
NSUserDefaults.standardUserDefaults().synchronize()

unfortunately user must restart the app! if anyone could find a solution to not restart the application please inform me.

I think KababChi's answer was right. However, in the newer versions of Swift NSUserDefaults has been substituted by UserDefaults. So the code would look like this:

UserDefaults.standard.set(languages[indexPath.row], forKey: "AppleLanguages")
UserDefaults.standard.synchronize()

App still needs to be restarted to apply these changes.