After the Xcode update, the compiler began to throw an error on the working code (both functions are in the AppDelegate.swift).
func application(application: UIApplication,
    didFinishLaunchingWithOptions launchOptions: NSDictionary?) -> Bool 
{
    FBLoginView.self
    FBProfilePictureView.self
    return true
}
With error:
/Users/../AppDelegate.swift:14:11: Objective-C method 'application:didFinishLaunchingWithOptions:' provided by method 'application(:didFinishLaunchingWithOptions:)' conflicts with optional requirement method 'application(:didFinishLaunchingWithOptions:)' in protocol 'UIApplicationDelegate'
And second
func application(application: UIApplication,        
                            openURL url: NSURL,
                            sourceApplication: NSString?,
                            annotation: AnyObject) -> Bool {
    var wasHandled:Bool = FBAppCall.handleOpenURL(url, sourceApplication: sourceApplication as! String)
    return wasHandled
}
with error
/Users/../AppDelegate.swift:25:11: Objective-C method 'application:openURL:sourceApplication:annotation:' provided by method 'application(:openURL:sourceApplication:annotation:)' conflicts with optional requirement method 'application(:openURL:sourceApplication:annotation:)' in protocol 'UIApplicationDelegate'
I understand that most likely I should like you to stick together somehow these two functions into one. I do not understand why this code suddenly stopped working in 6.3, despite the fact that it worked in 6.2.