Re: UndoManager

FROM : Dustin Voss
DATE : Mon Nov 18 07:25:38 2002

On Thursday, November 14, 2002, at 03:45  AM, Craig Bakalian wrote:

> Hi,
>     Still coding away at my music notation app.  I was just about finished
> the Data Model Classes when bam!, I realized I need redo and undo in
> the app.  I went for a walk through the SKTDrawDocument in the
> Sketch.app.  I think I understand how to register the selector and
> object with the NSUndoManager, yet in the Sketch.app I see this-
>
> - (void)insertGraphic:(SKTGraphic *)graphic atIndex:(unsigned)index {
>      [[[self undoManager] prepareWithInvocationTarget:self]
> removeGraphicAtIndex:index];
>      [_graphics insertObject:graphic atIndex:index];
>      [graphic setDocument:self];
>      [self invalidateGraphic:graphic];
> }
>
> This brings up many questions in my average IQ type head, firstly  I
> can't find the instance or function definition of undoManager that
> [self undoManager] , so is this an inherited method? I am assuming that
> [self undoManager] is a getter.  I mean, it has to be.  So, were is the
> get, in NSDocument?

It is actually declared in NSResponder. NSDocument and NSWindow both
override NSResponder's implementation to return an NSUndoManager, but
NSWindow checks its delegate first, which (in a document window) will
be NSWindowController, and NSWindowController will check with its
NSDocument instance.

(Disclaimer: This is from memory, so I may be wrong.)
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