15 Oct
2007
15 Oct
'07
7:24 a.m.
Does MANullAccessor have to be so so... erm unusable?
One important thing to notice is that the accessors are also used to
establish identity between descriptions. In case of the NullAccessor
this is done trough an UUID, in case of the SelectorAccessor this is
naturally done trough its selector.
If you happen to use it nothing seems to work with
it.
i.e. accessor selector doesnt work, one should argue that it shouldnt,
but is it doing a good job of being a null?
Since the NullAccessor is the default, it is supposed to warn the
user of a missing access strategy. In case descriptions are created
by end-users (where something like an access strategy would be out of
scope), the NullAccessor establishes a perfect identity, that can
then be used in #readUsing: and #write:using: to dispatch the access
for example to a dictionary.
Most users of read: dont test canRead: first.
I wonder if #canRead: and #canWrite: are still needed? Also most
access strategies seem to be useless to me. I only use the
NullAccessor (used internally), the ContainerAccessor (used
internally), the SelectorAccessor, and rarely the
AutoSelectorAccessor. Time for a clean-up?
I am thinking of implementing a subclass
MADummyAccessor which does
implement read: just so as it can play with the other accessors in
mementos etc.
That would make sense in your case, I guess.
Cheers,
Lukas
--
Lukas Renggli
http://www.lukas-renggli.ch