Cairngorm View Helper - Command resuability and tight coupling with view

Question

I am new to Cairngorm framework. Currently we are converting
our project to Cairngorm framework. I have some very basic doubts
regarding the framework. Basically I am a java/J2ee
programmer and got very good experience in struts framework
and other J2EE design patterns.
I have some doubts and needs advice from the community .
My very first doubt is regarding the ViewLocator pattern used
in the Cairngorm framework to access
the view from Command class. At a very high level my
understanding about command pattern is that command object
shouldn't know anything about the caller. Command should execute a
the business logic and update the model.
But if we use the ViewLocator pattern the command object
should know about it's caller class and the method name of the
view/viewhelper class which should be executed after the command
logic. In this scenario we will not be able to reuse the command
class and a very tight coupling is established between the command
and view.
I have read from flex and cairngorm related blogs about an
'Observer' and 'ChangerWatcher' patterns which seems to be right
approach for me rather than using the ViewLocator. But as far as I
know these are not part of the framework.
I would like to know what is the recommended approach from
the cairngorm framework team for executing View related logic after
firing the Cairngorm event.
If we use the ViewLocator pattern, there is no reusability as
far as the command is concerned and also a very tight coupling is
happening with the command and view.
Is this the right approach..?
Please advice..

Answer 1

Hi, the view Locator has very issues that we have to have in mind, y most of the  problems are similar when we are using the Drag Manager , when we are using modules and load this view dynamically.
The solution is simple and you told it. Binding by Watchers in the model Locator and checking the model locator variables when we load a module.
In the view that we want to change we can add a Change Watcher linking a model locator variable to a function in the view, we change the model in de command and automatically change the value in the view.
There are 2 ways to do the same concept, but is good only when the call to a cairngorm only affects the view that its calling it and known more has to know, so in theory you don’t need to change the model to impact the view.
First is adding a Iresponder in to the event by Get Set so in the view, when you create a event for cairngorm and have to pass through the event an IResponder  (mx.rpc.IResponder). When you are in the command in the result or fault you can do event.responder.result = event or event.responder.fault = event and this well go directly into the view result o fault. So you don’t have to pass through the model. (Responder is your get set in the Event of private var _responder:IResponder)
The other way is the same but using UM cairngorm that has CallBacks. And it’s pretty much the same but the event and all the cairngorm has callbacks and notifyCaller.
Well I hope I said something useful.
I did a UM cairngorm diagram in English http://www.developyourdream.net/tutoriales/tutoriales_flex_avanzados/cairngorm_universal_m ind/Cairngorm.swf
Sorry me English and if somebody talks Spanish you can go check my blog http://www.developyourdream.net/