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Home » Modeling » EMF "Technology" (Ecore Tools, EMFatic, etc)  » Undo of RecordingCommand is done in a strange order...
Undo of RecordingCommand is done in a strange order... [message #608576] Fri, 22 June 2007 18:11
Michael is currently offline MichaelFriend
Messages: 43
Registered: July 2009
Member
Hi.

I'm using RecordingCommand to catch changes in my EMF model and undo the=
m =

if needed. The model objects are also mapped to edit parts which hook em=
f =

change listeners into the model objects. When RecordingCommand is undone=
=

it issues that change events as undo is progressing. And i suddenly foun=
d =

that the order of events during undo of a bunch of EMF model changes is =
=

different to the reverse order of events that i receive when making thes=
e =

changes.

I've made some debugging and found that when i undo a RecordingCommand, =
it =

in turn undoes internal instance of CompositeChangeDescription.
CompositeChangeDescription contains list of ChangeDescription, being ask=
ed =

to undo it goes trough the list from the end and undoes each =

ChangeDescription.
This looks like correct unwinding of EMF changes, but surprisingly the =

list contains only one ChangeDescription that itself contains all the =

changes.
And the changes in list iside this single ChangeDescription are unwinded=
=

in the
order that is different from both strict and reverseing order of changes=
=

as they were performed before undoing... Well, maybe the resulting model=
=

will be ok after undoing all primitive changes in that other order, but =
=

the problem is that my edit part receives a notification during the undo=
=

and the model appears to be in wrong state at this moment.

Here is an example trace of the events. I have next structure from EMF =

objects:
topobject -> binding1 -> inst1 -> binding2 -> instr2 -> binding3.
Each of binding and bindingInstr objects has not-containment property =

named "type" that is set to ReferencedDesign1. ReferencedDesign1 itself =
is =

contained in a list property in the topobject. The action is to delete t=
he =

binding2 and to move it's child binding3 to bindInst1. And the action is=
=

made in signle transaction. Then the action is undone. Here are event =

lists (in format: "eventType: objectInstance.property =3D oldValue -> =

newValue):

While removing middle node:

REMOVE: instr1.bindings[0] =3D binding2 -> null
SET: binding2.parent =3D instr1 -> null

REMOVE: instr2.bindings[0] =3D binding3 -> null
ADD: instr1.bindings[0] =3D null -> binding3
SET: binding3.parent =3D instr2 -> instr1

REMOVE: binding2.instructions[0] =3D instr2 -> null
SET: instr2.type =3D ReferencedDesign1 -> null
SET: binding2.type =3D ReferencedDesign1 -> null

While undoing the remove:

SET: binding2.parent =3D null -> instr1
ADD: instr1.bindings[0] =3D null -> binding2

SET: binding3.parent =3D instr1 -> null
REMOVE: instr1.bindings[1] =3D binding3 -> null
ADD: binding2.instructions[0] =3D null -> instr2

SET: binding2.type =3D null -> ReferencedDesign1

SET: binding3.parent =3D null -> instr2
ADD: instr2.bindings[0] =3D null -> binding3

SET: instr2.type =3D null -> ReferencedDesign1


The incorrectness of undo order is obvious (binding2 on the first step o=
f =

undo is returned into containment hierarhy whereas it's type is not yet =
=

restored from null to ReferencedDesign1), please help...


PS. I'm using org.eclipse.emf.transaction_1.0.2.v200611161636.jar

-- =

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