Re: Undo group action name lost in drag operation
Re: Undo group action name lost in drag operation
- Subject: Re: Undo group action name lost in drag operation
- From: Gabriele de Simone <email@hidden>
- Date: Tue, 5 Oct 2004 11:32:47 -0400
On Oct 5, 2004, at 10:46 AM, Shaun Wexler wrote:
On Oct 5, 2004, at 6:33 AM, Gabriele de Simone wrote:
In response to a copy-on-drop operation in a NSTableView, I add a
number of elements to my model. To my great pleasure I noticed that
whatever Cocoa class was processing the drag operation for me was
automatically beginning and ending an undo group around my handler
(tableView:acceptDrop:row:dropOperation:).
Enlightened by this discovery, I set an action name at the end of my
insertions ("Add Items"), and sure enough this action name shows up
under the Edit menu as "Undo Add Items". The problems begin when you
undo that operation. The action name is lost, and the Redo menu item
name takes the name of the last nested action of the undo group.
Now, I did find the following workaround, which basically tells my
model objects *not* to set the action name if an undo group is
open...
if ([undoManager groupingLevel == 0) {
[undoManager setActionName:@"something"];
}
...but I am interested in knowing whether I am ignoring some basic
knowledge on undo grouping action names. A search for "undo group
action name lost" brought up nothing on CocoaBuilder.
It's best to set your action name in your controller class, in the
action method, etc. In your case where the model is handling the
drag/drop, it's okay to set the action name AFTER the drop is
completed. You definitely don't want to set action names for the
individual array accessor methods in the model. I create a separate
API for undoable model actions in the model itself, which set the
action name. Your undo invocation should call back into the array
accessors, not the separate API.
I may be misunderstanding your suggestion, but there is no controller
class where the drag is initiated and terminated from (it's
NSTableView, so everything is automatic if you implement a few
methods). I will try setting the action name outside
tableView:acceptDrop:row:dropOperation:, but my guts tell me that it
will require more bookkeeping (watch for some kind of drag-finished
notification? dig up what kind of operation was completed and set the
action name accordingly?)
In my experience I have found it convenient and appropriate to set the
action names at the model level, *if* you are also registering the
actual undo invocation there. With Bindings, often times there just
isn't any other controller/action code to set action names in. Any
controllers that sit above the model can still group actions together
and give them a better name anyway. The unexpected result here is that
the action name is lost.
Gabriele
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