How to manage Undo with multiple models linked together

Question

Hello,
I'm writing a java desktop application using MVC model. I'm using javax.swing.undo.UndoManager and related classes to manage the undo/redo capabilities. I know how to use it but I can't see how to implement it in a clean way when I have several models linked together. I hope someone can help...
I have 2 models M1 and M2. M2 depends on M1, so M2 listens to M1 changes.
Each model has its own view V1 and V2.
Model's methods which change the model's state create an UndoableEdit to restore the previous model's state.
UndoableEdits are combined together in a CompoundEdit created by the controller.
Upon a user action on V1:
1. M1 change
=> add UndoableEdit to current CompoundEdit
=> notify V1
=> notify M2
2. M2 change
=> add UndoableEdit to current CompoundEdit
=> notify V2
When we undo the CompoundEdit:
1. Undo M2 change
=> notify V2
2. Undo M1 change
=> notify V1
=> notify M2 !! PROBLEM
3. M2 change !! PROBLEM
=> notify V2 !! PROBLEM
And this is my problem: when undoing change on M1, I need to notify listeners (V1 and M2), but in this case M2 should not be notified because M2 has already restored its previous state in the CompoundEdit undo chain.
A solution might be to inhibit M2 listener if we're inside a undo/redo, but I feel it's not clean and not sure it will always work... Is there another way to solve this ? Or is it my architecture which is wrong ?
Thank you.
Edited by: gibi_31 on Aug 19, 2010 3:08 AM
Edited by: gibi_31 on Aug 19, 2010 3:11 AM

Answer 1

Hello,
Upon a user action on V1:
1. M1 change
=> add UndoableEdit to current CompoundEdit
=> notify V1
=> notify M2
2. M2 change
=> add UndoableEdit to current CompoundEditWhy?
Do you need to be able to undo the M2 change alone in any other case than undoing M1's change?
And if you don't add M2 change to the compound edit, doesn't the M2 update triggered by undoing the the M1 undo the M2 state automatically (thus performing the M2 undo)?
And this is my problem: when undoing change on M1, I need to notify listeners (V1 and M2), but in this case M2 should not be notified because M2 has already restored its previous state in the CompoundEdit undo chain.
A solution might be to inhibit M2 listener if we're inside a undo/redo, but I feel it's not clean and not sure it will always work...I agree it looks unclean (and quite dangerous actually if the app ever needs to support some form of multi-threaded model changes).
Regards,
J.