Am Di,05.08.2008 um 11:57 schrieb Uli Kusterer:
You may fire off observer methods too, which is probably undesirable.
Lucky then, that I adopted GNUstep-style ASSIGN() and DESTROY()
macros for these purposes, and since most of my code still needs to
be 10.4-compatible, I've mostly been using those:
<http://www.zathras.de/angelweb/sourcecode.htm#UKHelperMacros>
Though I vaguely remember getting lectured by someone about why it's
better to *always* use the accessors a while ago ... wish I
remembered what the reasoning behind that was, and why I thought it
might be a good idea to follow that, but OTOH didn't follow it :-/
The advantages are:
- You have only one place per property, which handles the memory
management. Just imagine, that you change the type of reference from
hard to weak. You have to handle that change only inside the setter.
- You have side-effects you want to use at deallocation time, too: the
property refers to something "outside", which has to be deallocated,
turn of, … manually. Think of a guard wiith property that adds
observations to another object. Changing the proprety (the referred
object) in any case (including the case of deallocation) should delete
the observation. So the settter is a single place, where you can
handle it.
disadvantages:
- side-effects at dellocation time, which you do not want to use: I
mentioned undo registration.
But I think, that the problem figured out by Ken (being observed in -
dealloc), does not exist . Observations has to be removed by every
object which sends a retain to an instance Before the deallocation
takes place (-dealloc is called after a -retain) the obseving object
already had to be removed. If there is still an observation of an
object running through -dealloc, you have another problem. No observed
object should disappear.
My 0,05 $
Amin
Cheers,
-- Uli Kusterer
"The Witnesses of TeachText are everywhere..."
http://www.zathras.de
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