Can I disable custom keyboards (iOS8) for my app?

Question

EDIT: tl;dr - it is possible, see accepted answer below.

Is there any (not only programatic) way of preventing custom keyboards (iOS8) from being us

Answer 1

Swift 3 :

func application(_ application: UIApplication, shouldAllowExtensionPointIdentifier extensionPointIdentifier: UIApplicationExtensionPointIdentifier) -> Bool {
    if extensionPointIdentifier == UIApplicationExtensionPointIdentifier.keyboard {
        return false
    }
    return true
}