Re: How to design async widget
Thanks a lot, Gregor, for such full answer, and thanks for link About Controller, i meant that i want to separate business of creating item in group widget and removing from it from widget itself - it is only visual representation of list of groups. It only know that he can hold group, provide interface to manage it, but what exactly happen with group - it doesn't matter for widget. What works simplest usually works best. - gold phrase . Thanks Now, i provide two methods for some business action with group - first one notifies client app that widget created some group, calling controller method with newly created group as parameter - and second simple method to add new group to widget. So Controller implementor decides what to do with that request for group creation On 2 дек, 20:45, gregor [EMAIL PROTECTED] wrote: 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 fromwidget.. 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/threa... 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 awidgetof 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 forWidget(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 fromwidget 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 inwidgetevent handler, but i want to separate this transport/business layer fromwidget. Mywidgetsimply 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 forwidgetclient - 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 ListGroup 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).
Re: How to design async widget
I think it depends on this question: How many views (i.e. primary widgets) in your app need to know about Groups (and therefore need to get notified if a group is added, deleted or changed)? If the answer is one, then the simplest answer is to integrate the Create Group dialog into it and move ListGroup groups into it as well. The create group dialog could be a pop up, disclosure panel, whatever, and an inner class of this view. Job done. However if the answer is more than one then you probably do need to do what have been suggesting, i.e. you need to separate Groups out and treat them as part of an application Model independent from the Views. I think a reasonably classical way to go about this is as follows: 1) You have a Controller that has method ListGroupgetGroups(). This method checks if the groups have already been loaded and if not executes RPC to get them before returning the group list. It maintains reference to this list (which is now part of the model). 2) Create Group widget calls this method to get existing groups for its display, and if a new group is created, it calls a second method Controller.addGroup(Group group). 3) Controller.addGroup(..) calls the RPC service to add group to server model, and if successful adds the new group to the Group list (the model). 4) At this point Controller.addGroup() (or possibly the Group list itself) fires an Event announcing the change. Many people refer to this as something like a PropertyChangeEvent. So Controller (or possibly as I say the Group List model object itself) implements a SourcesPropertyChange interface, and the views implement a PropertyChangeListener interface. 5) The views are then registered as PropertyChangeListeners either with Controller or via Controller with individual model classes (e.g. Group List). 6) They will now all have a method (say) onPropertyChanged (PropertChangeEvent event) from which they can call Controller.getGroups() again to refresh their displays with the new data. If you have more than one model object that gets handled like this the question arises as how the listeners (i.e. the views) know which one has changed. Indeed, if your app has a lot of views the question also arises as to whether they all need to get notified of every event. As things get more compilcated, you run the risk of creating an event storm that slows the app's responsiveness. There are various ways of dealing with both issues, for example. a) if ProperrtChangeEvent is equipped with an enum of possible events (ADD_GROUP,ADD_SOMETHING_ELSE,...,ACTION_A_PERFORMED ETC), client views can conveniently use a switch statement in their onPropertyChanged(...) methods to determine if they need to respond to an event and to ask controller for the appropriate model objects if they do.. b) you can use sub classes to create different listener interfaces and event classes to deal with different functional areas of the application, and thereby fine tune which views need to listen to which model changing events thereby reducing the overall number of events processed. This sort of thing isn't directly supported in 1.5.x (you really have to write it yourself, but you can sort of copy e.g. ChangeListener stuff), but the new GWT event model (due I believe in 1.6 and available now via svn in trunk) is much more suited to supporting this idea. Check out incubator: http://code.google.com/p/google-web-toolkit-incubator/wiki/ProposedEventSystem Anyway I hope this has given you as few ideas, and also explains why I suggested you should make sure you really do need to do this. regards gregor On Dec 3, 9:55 am, raxelo [EMAIL PROTECTED] wrote: Thanks a lot, Gregor, for such full answer, and thanks for link About Controller, i meant that i want to separate business of creating item in group widget and removing from it from widget itself - it is only visual representation of list of groups. It only know that he can hold group, provide interface to manage it, but what exactly happen with group - it doesn't matter for widget. What works simplest usually works best. - gold phrase . Thanks Now, i provide two methods for some business action with group - first one notifies client app that widget created some group, calling controller method with newly created group as parameter - and second simple method to add new group to widget. So Controller implementor decides what to do with that request for group creation On 2 дек, 20:45, gregor [EMAIL PROTECTED] wrote: 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 fromwidget.. 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:
Re: How to design async widget
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 ListGroup 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 GUI widget that will help me to add and delete
some business groops
like this.
public class GroupWidget extends Composite implements ClickListener {
private Controller controller;
private ListGroup groups;
public GroupWidget(ListGroup groups, Controller
controller) {
this.controller = controller;
//build widget skeleton
//init structures
}
public void onClick(Widget sender) {
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 this widget will use async requests, so
methods in controller must have void as
a return type, but how can i notify widget that group is created ?
Should i add such methods to widget
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
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Re: How to design async widget
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 ListGroup 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 ListGroup groups;
public GroupWidget(ListGroup 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.
To post to this group, send email to Google-Web-Toolkit@googlegroups.com
To unsubscribe from this group, send email to [EMAIL PROTECTED]
For more options, visit this group at
http://groups.google.com/group/Google-Web-Toolkit?hl=en
-~--~~~~--~~--~--~---
How to design async widget
First of all sorry for my english.
I want to write simple GUI widget that will help me to add and delete
some business groops
like this.
public class GroupWidget extends Composite implements ClickListener {
private Controller controller;
private ListGroup groups;
public GroupWidget(ListGroup groups, Controller
controller) {
this.controller = controller;
//build widget skeleton
//init structures
}
public void onClick(Widget sender) {
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 this widget will use async requests, so
methods in controller must have void as
a return type, but how can i notify widget that group is created ?
Should i add such methods to widget
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.
To post to this group, send email to Google-Web-Toolkit@googlegroups.com
To unsubscribe from this group, send email to [EMAIL PROTECTED]
For more options, visit this group at
http://groups.google.com/group/Google-Web-Toolkit?hl=en
-~--~~~~--~~--~--~---
Re: How to design async widget
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=gstq=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 ListGroup 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 ListGroup groups;
public GroupWidget(ListGroup 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...
