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[EMF] [CommandStack] Best Practices to use ChangeCommand around UI Dialog [message #900231]

Sun, 05 August 2012 18:08

Eclipse User

I try to do this:
- To change an EMF model object by an UI Dialog (jface TitleAreaDialog)
- To register the changes in the CommandStack only if user does a click in the Ok Button of the Dialog
- To undo the possible changes in the dialog if user does a click in the Cancel Button (not register the changes in the CommandStack)

To register the changes, I use ChangeCommand.
My Code is more or less the next:

Collection<Notifier> objectsToRecord = new ArrayList<Notifier>();
objectsToRecord.add(objectToRegisterChanges);
cancel = false;
ChangeCommand changeCommand = new ChangeCommand(objectsToRecord) {
   @Override
   protected void doExecute() {
      CustomDialog editorDialog =  new CustomDialog(
         PlatformUI.getWorkbench().getActiveWorkbenchWindow().getShell(), SWT.NONE,
         objectToRegisterChanges);
      editorDialog.create();
      if (editorDialog.open() != Window.OK) {
         cancel = true;
      }
   }
};
getCommandStack().execute(command);
if(cancel) {
   getCommandStack().undo();
}

objectToRegisterChanges is an EMF Object
CustomDialog extends JFace TitleAreaDialog where attributes and list belong to objectToRegisterChanges are changed
getCommandStack() returns my own BasicCommandStack

Even if user does a click in Cancel Button, the changes in the objectToRegisterChanges are added to CommandStack by the ChangeCommand. My code logically does the undo in this case but the command is on the top of the CommandStack and it can be redo

Does someone say to me the best solution for my situation or guide me??

Re: [EMF] [CommandStack] Best Practices to use ChangeCommand around UI Dialog [message #900243 is a reply to message #900231]

Mon, 06 August 2012 03:02

Eclipse User

Commands should be executed AFTER the user has presses OK in your dialog. That could look something like this:

CustomDialog editorDialog =  new CustomDialog(..., objectsToRecord);
editorDialog.create()
if (editorDialog.open() == Window.OK) {
    ChangeCommand changeCommand = new ChangeCommand(objectsToRecord);
    getCommandStack().execute(command);
}

Re: [EMF] [CommandStack] Best Practices to use ChangeCommand around UI Dialog [message #900266 is a reply to message #900243]

Mon, 06 August 2012 05:18

Eclipse User

Christoph, Thank for your answer but I think it does not work.
I know the correct way to put Command in the stack is after Ok pressing but two things:
- ChangeCommand is an abstract class that needs a doExecute method where the changes must be produced (or at least I think so)
- If user cancels the dialog, we have to undo all possibles changes (in the dialog, I like to use EMF databinding so changes in UI components are automatically reflected in the attributes of the model object)

Re: [EMF] [CommandStack] Best Practices to use ChangeCommand around UI Dialog [message #900299 is a reply to message #900266]

Mon, 06 August 2012 08:07

Eclipse User

Hi Paco

my approach to this is:
- copy the object to edit (detached from the resource)
- let the user edit all he likes in the dialog or wizard
- on cancel: do nothing (because the original object is unchanged)
- on ok: use an emf command to copy the changed attributes to the original object

I only use undo() if the user chooses the undo-action in the menu or toolbar.

Greetings
Christoph

Re: [EMF] [CommandStack] Best Practices to use ChangeCommand around UI Dialog [message #900318 is a reply to message #900299]

Mon, 06 August 2012 09:05

Eclipse User

Christoph,

Yes, that sounds better.

On 06/08/2012 2:07 PM, Christoph Keimel wrote:
> Hi Paco
>
> my approach to this is:
> - copy the object to edit (detached from the resource)
> - let the user edit all he likes in the dialog or wizard
> - on cancel: do nothing (because the original object is unchanged)
> - on ok: use an emf command to copy the changed attributes to the
> original object
>
> I only use undo() if the user chooses the undo-action in the menu or
> toolbar.
>
> Greetings
> Christoph

Re: [EMF] [CommandStack] Best Practices to use ChangeCommand around UI Dialog [message #900332 is a reply to message #900299]

Mon, 06 August 2012 10:17

Eclipse User

Yep, I'd do it the same way. Another reason why I like to only change the model if the user selects okay is because if other clients (e.g., views, editors, etc) are using the same data they will reflect those changes even though the changes might not be permanent. This could cause those views to trigger webservices, etc.

Re: [EMF] [CommandStack] Best Practices to use ChangeCommand around UI Dialog [message #900347 is a reply to message #900332]

Mon, 06 August 2012 10:53

Eclipse User

We are directly executing the changes on the model, because our
validation system can not do cross object validations without it.

Our approach is that we've customized the EditingDomain so that we can
set a SavePoint on it (similar to what you do with a database), if the
user hits cancel we simply rollback to the save point.

In pseudo code we do:

ISavePointEditingDomain d = ....
SavePoint p = d.createSavePoint();

TitleAreaDialog d = ....
if( d.open() == Window.OK ) {
p.dispose();
} else {
p.rollback();
}

Tom

Am 06.08.12 16:17, schrieb John Steele:
> Yep, I'd do it the same way. Another reason why I like to only change
> the model if the user selects okay is because if other clients (e.g.,
> views, editors, etc) are using the same data they will reflect those
> changes even though the changes might not be permanent. This could cause
> those views to trigger webservices, etc.

Re: [EMF] [CommandStack] Best Practices to use ChangeCommand around UI Dialog [message #900358 is a reply to message #900347]

Mon, 06 August 2012 11:33

Eclipse User

Step by step:
- Christoph / John. You are right that changes in the model are automatically reflected in other views/editors with databinding. In my case, I use CDO to manage model modifications so other clients/views/editors have their own CDO instance that are only refreshed when a commit is executed.
1) My model object has a list, not more than 10 items inside. But do you considerer the copy of the object is the better way if you have a list with 1000 items?

- Thomas, savePoint could give a solution but
2) where is the commandStack to undo/redo the changes? Because if user hits Ok, we want to give him the possibility of undo/redo these changes.

My new code that works Razz

Collection<Notifier> objectsToRecord = new ArrayList<Notifier>();
objectsToRecord.add(objectToRegisterChanges);
ChangeRecorder changeRecorder = new ChangeRecorder();
changeRecorder.beginRecording(objectsToRecord);
CustomDialog editorDialog =  new CustomDialog(..., objectToRegisterChanges);
editorDialog .create();
int respond = editorDialog.open();
MyChangeCommand changeCommand = new MyChangeCommand(changeRecorder, objectsToRecord) {
   @Override
   protected void doExecute() {}
};
if (respond == Window.OK) {
   getCommandStack().execute(changeCommand);				    	
} else {
   changeCommand.execute();
   changeCommand.undo();
}


....


abstract class MyChangeCommand extends ChangeCommand {
  public MyChangeCommand(ChangeRecorder changeRecorder, Collection<Notifier> notifiers) {
     super(notifiers);
     this.changeRecorder = changeRecorder;
  }
		
  @Override
  public void execute() { 
     ChangeRecorder changeRecorder = getChangeRecorder();
     if (changeRecorder == null) {
        changeRecorder = createChangeRecorder();
        changeRecorder.beginRecording(notifier != null ? Collections.singleton(notifier) : notifiers);
     }
     try {
        doExecute();
     } finally {
        setChangeDescription(changeRecorder.endRecording());
        disposeChangeRecorder(changeRecorder);
     }    
  }  
}

What is your opinion?

[Updated on: Mon, 06 August 2012 11:41] by Moderator

Re: [EMF] [CommandStack] Best Practices to use ChangeCommand around UI Dialog [message #900410 is a reply to message #900358]

Mon, 06 August 2012 17:42

Eclipse User

So you want to undo those changes in one big undo instead of step by
step ones?

Tom

Am 06.08.12 17:33, schrieb Paco Blanco:
> Step by step:
> - Christoph / John. You are right that changes in the model are
> automatically reflected in other views/editors with databinding. In my
> case, I use CDO to manage model modifications so other
> clients/views/editors have their own CDO instance that be only refreshed
> when a commit is executed.
> 1) My model object has a list, not much than 10 items inside. But do
> you considerer the copy of the object is the better way if you have a
> list with 1000 items?
>
>
> - Thomas, savePoint could give a solution but 2) where is the
> commandStack to undo/redo the changes? Because if user hits Ok, we want
> to give him the possibility of undo/redo these changes.
>
>
> My new code that works :p
>
> Collection<Notifier> objectsToRecord = new ArrayList<Notifier>();
> objectsToRecord.add(objectToRegisterChanges);
> ChangeRecorder changeRecorder = new ChangeRecorder();
> changeRecorder.beginRecording(objectsToRecord);
> CustomDialog editorDialog = new CustomDialog(...,
> objectToRegisterChanges);
> editorDialog .create();
> int respond = editorDialog.open();
> MyChangeCommand changeCommand = new MyChangeCommand(changeRecorder,
> objectsToRecord) {
> @Override
> protected void doExecute() {}
> };
> if (respond == Window.OK) {
> getCommandStack().execute(changeCommand);
> } else {
> changeCommand.execute();
> changeCommand.undo();
> }
>
>
> ...
>
>
> abstract class MyChangeCommand extends ChangeCommand {
> public MyChangeCommand(ChangeRecorder changeRecorder,
> Collection<Notifier> notifiers) {
> super(notifiers);
> this.changeRecorder = changeRecorder;
> }
>
> @Override
> public void execute() { ChangeRecorder changeRecorder =
> getChangeRecorder();
> if (changeRecorder == null) {
> changeRecorder = createChangeRecorder();
> changeRecorder.beginRecording(notifier != null ?
> Collections.singleton(notifier) : notifiers);
> }
> try {
> doExecute();
> } finally {
> setChangeDescription(changeRecorder.endRecording());
> disposeChangeRecorder(changeRecorder);
> } } }
>
>
> What is your opinion?

Re: [EMF] [CommandStack] Best Practices to use ChangeCommand around UI Dialog [message #900512 is a reply to message #900410]

Tue, 07 August 2012 06:43

Eclipse User

Yes, I do. It is my approach. (Inside the dialog, we can put step by step undo/redo of each change. When users exists, all of them must be in an only command)

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