Hi Rexalo, My 2c. What you seem to asking is if there is a standard "right" way to do Model-View-Controller with GWT and/or what is the "best" way to, as you put, "separate this transport/business layer from widget.". IMO the answer is that there isn't a standard one, rather several options or approaches. But I would search the group for "MVC" to get a flavour of how many different opinions there are about this. Check this discussion, for example, which is top of the list:
http://groups.google.com/group/Google-Web-Toolkit/browse_thread/thread/6588acb2e9afe9d9/23f6dda583eaa44f?lnk=gst&q=MVC#23f6dda583eaa44f IMO the difficulty is that both "Controller" and "Model" are slippery concepts in an AJAX web application, whereas "View" is a straight forward concept - it's a widget of some kind. Some reasons are: 1) The real "Controller" in an AJAX application is the browser - anything involving a change to the DOM ultimately runs through its event queue (and it also handles request dispatches and fields the responses as well), therefore it is natural for Widget (i.e. view) classes to interact with the browser event queue directly, and this is what GWT does. Because GWT widgets catch, process and sink events routinely anyway it is difficult (but not impossible) to separate them from a separate "Controller" in a clean or meaningful way. 2) What might we mean when we refer to a "Model" maintained client- side in a GWT application? Is it the "real" domain model for the application, some sub-set of it, or maybe a snapshot of some some sub- set of it? If you think about it, the "real" domain model resides on the server and ultimately whatever sub-set of this is transported to the GWT client must at some point be reconciled with the "real" server model (i.e. the one actually persisted to backing store) always bearing in mind that another client might have changed the "real" model independently in the meantime. Both these issues can introduce significant complexity. This is not to say that there are not sometimes good reasons to introduce "Controllers" and "Models" client side. An example might be a chat application that uses blocking requests (i.e. comet style) to pick up new messages. But it does imply that doing so introduces layers of complexity to a GWT application that may be unnecessary. For these reasons I don't think it is automatically the case that "i want to separate this transport/business layer from widget" is a necessarily a good design/engineering decision in a GWT app. What works simplest usually works best. However, sometimes it is and there are several approaches to doing it - it depends on what you are actually trying to achieve, not on a matter of (MVC) principle. regards gregor On Dec 2, 1:01 pm, raxelo <[EMAIL PROTECTED]> wrote: > Hi, Gregor! > Thanks forreply. > > I understand that i can't simply use rpc call right in widget event > handler, > but i want to separate this transport/business layer from widget. > > My widget simply shows list of items of some class(Group) and provide > control elements > to manupulate them: edit, delete, add etc. > > I am simply interested in a approach. maybe there is some standart way > advices > > For now - i provide two methods for widget client - > void add(Group) > void onAdd/onSuccessAdd(Group) > > maybe there is some more cultural way ? =) > > On 2 дек, 13:37, gregor <[EMAIL PROTECTED]> wrote: > > > Hi Relaxo, > > > The simplest way is to make your RPC call from addBtn.onClick() using > > an anonymous Callback where this callback's onSuccess(..) method adds > > the new Group List<Group> groups and changes the view as required. > > There may be reasons why this would not meet your requirements, but it > > is not possible to say from your example, i.e. on the face of it you > > do not need the controller interface. There isn't a single "right" way > > to do asynchronous RPC - it is possible to over-engineer it and > > equally it's possible to under-engineer it. > > > If in fact your situation is more complicated than the example > > (leading to a motivation for using this controller interface), > > probably best to give some idea of the overall problem to get further > > advice and options (of which there are several). > > > regards > > gregor > > > On Dec 2, 8:15 am, raxelo <[EMAIL PROTECTED]> wrote: > > > > First of all sorry for my english. > > > > I want to write simple GUIwidgetthat will help me to add and delete > > > some business groops > > > like this. > > > > public class GroupWidget extends Composite implements ClickListener { > > > private Controller controller; > > > private List<Group> groups; > > > > public GroupWidget(List<Group> groups, Controller > > > controller) { > > > this.controller = controller; > > > //buildwidgetskeleton > > > //init structures > > > } > > > > public void onClick(Widgetsender) { > > > if(sender == addBtn) { > > > //creating group object using entered date > > > such as name, picture etc... > > > this.controller.add(group); > > > } > > > } > > > > static interface Controller { > > > Group add(Group group); > > > void delete(Group group); > > > } > > > > } > > > > but, i can't understand how it must work with async requests > > > > Application that will use thiswidgetwill use async requests, so > > > methods in controller must have void as > > > a return type, but how can i notifywidgetthat group is created ? > > > Should i add such methods towidget > > > onAdd(Group newlyCreatedGroup) and > > > onDelete() , that controller implementor have to call after receiving > > > a response or maybe there is some > > > approach or pattern. > > > > Thanks a lot --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Google Web Toolkit" group. 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