Re: Non-standard attributes - avoid warning from data model compiler?
Re: Non-standard attributes - avoid warning from data model compiler?
- Subject: Re: Non-standard attributes - avoid warning from data model compiler?
- From: Dan Messing <email@hidden>
- Date: Wed, 1 Jun 2005 12:08:18 -0500
Unless I'm missing something, we're actually saying the same thing,
right? I guess my question is this: does adding a transient attribute
for a non-standard (say, an NSRect) attribute provide any
functionality beyond automatic undo/redo support?
Or remove the transient attribute, which I believe will only break
undo/redo, which you would then have to implement yourself for the
custom attribute. I'm no authority on the subject though, so
someone please correct me if I'm wrong here.
A transient attribute will not break undo/redo. In fact, the main
reason to use a transient attribute is to have an attribute that
isn't persistent but is nonetheless managed.
One use for a transient attribute is to represent a value type
(class) that Core Data doesn't natively support — such as NSColor
or one of your own value classes — and use a persistent attribute
as "backing store" for it. Another use is for a derived attribute
that you want to appear in your model, because you have code that
walks your model, or because you want to drop your entity on IB to
generate an interface or a controller. In the former case you'd
get undo/redo support for your attribute, in the latter it would be
effectively read-only.
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