Re: binding to number of selected rows in a table [solved]
Re: binding to number of selected rows in a table [solved]
- Subject: Re: binding to number of selected rows in a table [solved]
- From: Jerry Krinock <email@hidden>
- Date: Wed, 4 Mar 2009 16:38:24 -0800
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.
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.
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