On Sep 8, 2008, at 4:27 PM, Florijan Stamenkovic wrote:
On Sep 08, 2008, at 18:48, Chuck Hill wrote:
Primary keys.
Oh yeah. That makes sense too... Hm, do you know if EOF throws a
validation exception when trying to modify a read only attribute?
Yes. If you make your FK attributes public you will get this
exception when saving updates. It is kind of wrong in that case, but
many people have seen this "Attempt to modify a read only attribute"
error message.
IIRC there was talk against making primary keys class properties,
one of the arguments being that one should never modify them. But,
if they are read only, and EOF throws, then that would not have been
possible, no?
Personally, I don't have any issues with public primary keys as long
as they are used responsibly. The objection is usually either
religious or out of fear of irresponsible use. EOF will NOT let you
change them.
You can also mark them as such in the model to have EOF verify
there have not been any changes.
I am guessing that (if EOF indeed does not accept modifications of
RO attributes) the purpose of this is to preserve existing data, and
in situations in which data is created outside of EOF?
I think you can create new objects with these attributes assigned a
value. You just can't change it afterwards.
Chuck
On Sep 8, 2008, at 3:46 PM, Florijan Stamenkovic wrote:
Hi all,
I'm looking into EOAttribute.isReadOnly(). Docs point out that an
attribute is read only when it is derived (makes sense), but
mention no other circumstance. So, anyone knows any other
situation in which an attribute is read only?
Thanks,
F
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Chuck Hill Senior Consultant / VP Development
Practical WebObjects - for developers who want to increase their
overall knowledge of WebObjects or who are trying to solve specific
problems.
http://www.global-village.net/products/practical_webobjects
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