Employing GWT's RequestFactory within Activities - gwt

Question

My CustomerActivity class happens also to be a presenter in the MVP sense. In response to actions by the user, the following code is called:
context.update(customer).fire(new Receiver<CustomerProxy>() {
public void onSuccess(CustomerProxy response) {
// set the view according to the response
}
});
When the above code executes, two things happen:
I receive an updated copy of the Customer, with which I can refresh the state of the view
An EntityProxyChange event is fired
The CustomerActivity listens for EntityProxyChange events because other Activities also make changes to customer records, and I want to keep the CustomerActivity up-to-date.
EntityProxyChange.registerForProxyType(eventBus, CustomerProxy.class,
new EntityProxyChange.Handler<CustomerProxy>() {
public void onProxyChange(EntityProxyChange<CustomerProxy> event) {
fetchCustomer(event.getProxyId());
// ...but what if it was me that made the change?
}
});
Since theupdate method already returns an up-to-date Customer, I don't need to fetch the customer again during processing of the EntityProxyChange; and I don't want to incur the cost of another call to the server if I can avoid it.
I was hoping that the EntityProxyChange class would provide me with the entity's version number, which I could compare with the version of the customer I have cached. No dice.
I suppose I can set some kind of inTheMiddleOfAnUpdateOperation flag, and check it before fetching the customer. Is that what people are doing? The idea makes me gag just a little bit. Can you suggest a better way to write an activity that listens for changes and makes changes to the same entity types?

Answer 1

I'm not sure this would work, but you could try to create another event bus :
final EventBus customerActivityEventBus = new SimpleEventBus();
Initialize a new RequestFactory with this eventBus and use it in the CustomerActivity.
customerActivityRequestFactory = GWT.create(CustomerRequestFactory.class);
customerActivityRequestFactory.initialize(customeActivityEventBus);
CustomerRequest context = customerActivityRequestFactory.customerRequest();
Your CustomerActivity will still listen to change events from the main eventBus but will not see the events it fired.
In your other activities, listen to events either only from the customerActivityEventBus or from both, depending on what you want.
Of course, keep only one main eventBus to use for events that are not from a Request Factory (ie. ActivityManager, PlaceHistoryHandler, etc ..)