I tried to add some custom event when Image tracking in different conditions , so I make some change in MARSession. I turn m_Subscriber from readonly to public , so I can get it , then , I access m_Subscriber to my script : Code (CSharp): MARS_instance.m_Subscriber.SubscribeMarkerUpdated (customMarkerUpdateEvent); It work fine in editor , but not work in iOS. When I trigger this line , it show this on Xcode [B]Uploading Crash Report NullReferenceException: Object reference not set to an instance of an object.[/B] And I find out , m_Subscriber is null when I run in iOS , but it exist in the editor . Is there anyway to find it? Many thx!