passing parameters from one presenter to another with GWT-Platform

Question

I'm trying to pass a parameter that I have loaded on a presenter to another presenter, a car from some client, for example.

What's the best way to do this? Using the gatekeeper? Any example?

PS: I using DI with gin and the GWT-Platform framework.

Tat

If the state for the 2nd presenter should be bookmarkable you can use prepareFromRequest(PlaceRequest) to handle parameters. In your 1st presenter you use PlaceManager.revealPlace(PlaceRequest) with a newly generated PlaceRequest containing the parameter. – Mushy

Answer 1

If the presenter should be loaded when the event is fired you can use a ProxyEvent. Have a look at http://code.google.com/p/gwt-platform/wiki/GettingStarted?tm=6#Attaching_events_to_proxies and http://arcbees.wordpress.com/2010/08/31/using-proxyevent/.

Mushy

Answer 2

If you want to reduce coupling, you should create a custom event, CarLoadedEvent or something. Use GWTP Plugin for that, it works great. Then have your presenter that wants to catch that event implement CarLoadedHandler, and in its onBind() method, make it register to the eventBus :

@Override
protected void onBind() {
super.onBind();
registerHandler(getEventBus().addHandler(CarLoadedEvent.TYPE, this));
}

Finally, when a car is loaded, fire an event :

CarLoadedEvent.fire(getEventBus(), myLoadedCar);

Escapee

Agreed w/ Mikael. I have several examples in my code at github.com/dartmanx/mapmaker/tree/0.5.2 in the client package. I used GWT-Platform as well. – Seamus

and how i do it if my other presenter is not visible yet? – Tat

Haha, I didn't see it that way ! In the case the next presenter hasn't been instantiated yet, I'd just pass the ID of the car as a URL parameter (see comment of your question by z00bs), and the request the car to the server. – Escapee

haha, yea, I've not explain right my question, i just don't want to load it multiple times.. do you have another suggestion? – Tat

I decide to pass the id by PlaceRequest and it worked, and, thinking about other things, like maintain the object updated, i will use this way. Well, like no one else said anything, I will vote for the only answer. Thank you mikael-couzic. – Tat

Answer 3

See GWTP doc & blog:

• for regular Event handling
• for Event handling that should wake up another Presenter not yet initialized/showing
• boilerplate code generation related to simplifying coding Event handling

Digitalism