Jerry Krinock wrote:
On 2009 Mar 04, at 11:39, James Walker wrote:
* Add an NSMutableIndexSet* member to my controller, to store the
selection.
* Add KVO-friendly accessors for that index set.
* Update the index set (using the setter) in the
outlineViewSelectionDidChange: delegate method.
James, you've added an instance variable which is simply a copy of other
data. This is always a dangerous practice that must be exercised with
great care. Although this practice is occasionally necessary for
performance reasons, other alternatives should be considered first. In
my judgment, getting KVObservability for a variable is not a enough good
reason.
For brevity, I didn't tell the whole story. Contrary to what I said in
my original post, what I really needed was not all the selected rows,
but just the ones at the lowest level of the hierarchy. So in my
outlineViewSelectionDidChange: method, I'm not just copying the result
of [NSOutlineView selectedRowIndexes], but computing a subset.
But your comments are interesting, thanks.
Maybe you'll be able to get away with it this time, because it's just an
index set, but don't make a habit of this. If you ever try this with,
for example, Core Data managed objects, you'll be spending some time
bug-hunting.
I'm sticking with my method.
--
James W. Walker, Innoventive Software LLC
<http://www.frameforge3d.com/>
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