Hello Marco,
The slot method was called but I found the sender was null. Is that correct?
yes, this is correct. I have just discovered that our documentation incorrectly mentions notifyobservers in context of sender built-in variable. We have to correct it. When using notifyobservers, no sender information is propagated to prevent strong references to the sender object.
As alternative: see the System Event and System Event Handler. They provide a more powerful 'broadcast event' functionality and you can attach a context data to the event. The context data could be the sender in this case. Even if System Event is described in context of the Device Interface, it is very well suitable for inter-application events.
The difference between System Event and notifyobservers is: System Event manages internally a queue and each time you trigger the System Event, new event will be broadcasted to all associated handler. In other words, when you trigger System Event tree times in succession, you will receive tree notifications.
notifyobservers, in turn, accumulate the events triggered during current screen update and causes only one common event to be delivered to the associated observers.
I hope it helps you further.
Best regards
Paul Banach
