To receive logs from SpikeSDK, use the following code: 
Spike.setLogCallback { level, message in
    print("\(message)")
}
If you are using background delivery, ensure this code runs in your application’s didFinishLaunchingWithOptions method before you start using SpikeSDK: 
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    ...
    Spike.setLogCallback { level, message in
        print("\(message)")
    }
    Spike.configure()
    ...
}