15 Oct
2007
15 Oct
'07
2:27 a.m.
Does MANullAccessor have to be so so... erm unusable?
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?
Most users of read: dont test canRead: first.
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.
I just wondered if there was a case for making MANullAccessor more
friendly, i.e. swap its behaviour from pessimistic to optimistic, rather
than expecting all users to test canRead: first, expect those users that
really care to test cantRead:
just an idea
Keith
15 Oct
15 Oct
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
10:25 a.m.
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 think the ChainAccessor strategy is also very useful> From:
renggli(a)iam.unibe.ch> Subject: Re: MANullAccessor> Date: Mon, 15 Oct 2007 07:24:04
+0200> To: smallwiki(a)iam.unibe.ch> > > 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> > >
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noon
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 think the ChainAccessor strategy is
also very useful
2:35 p.m.
Lukas Renggli wrote:
Agree, but I found myself to prefer helper methods. For example
instead of specifying #(group name) using a ChainAccessor, I just
implemented User>>#groupName that delegates to the group and then use
the SelectorAccessor. There are certainly cases where the
ChainAccessor is simpler to use.
Lukas
I use MAChainAccessor as a fundamental piece in my RDB mapping.
I walk the descriptions, including OneToOne relations and build a
mapping from a flat db response into the described object model. As I
build the query I collect the accessors for writing the query results
into the model.
While doing this I treat the Chain accessors like a stack that you can
push and pop onto. I add MAAccessor-chainTo: for pushing and
chainUnlinkLast for popping with #isChainAccessor for testing along the way.
I have used MADictionaryAccessor for accessing settings but ended up
defining a first class object for this.
I use BlockAccessor for situations where the DB is not quite mapping
directly into the to/from the model
Now I have DummyAccessor, which works very well, since I only have to
define #defaultAccessor - I have a table component where I select the
content and order of fields for columns. However I also define buttons
and spacers with descriptions even though they have no values, they can
be selected and ordered together with real value accessing items.
So I am not sure there is much left to tidy up....
Keith
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 think the ChainAccessor strategy is also very useful
6032
days inactive
6032
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4 comments
3 participants
participants (3)
-
isaiah perumalla -
Keith Hodges -
Lukas Renggli