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Rob Kinyon wrote:
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cite="mid:70384420903050917j69e76d90h70c10035719dae9d@mail.gmail.com"
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<pre wrap="">On Thu, Mar 5, 2009 at 12:07, David Ihnen <a class="moz-txt-link-rfc2396E" href="mailto:davidi@norchemlab.com"><davidi@norchemlab.com></a> wrote:
</pre>
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<pre wrap="">Nothing is actually a plugin that impliments the 'Nothing' design pattern -
that is - instead of returning null when referencing a row in an empty
resultset (particularly ->single and ->first, which I use many times when
NOT looping over results, hence resulting in undef dereference errors on
empty) it instead returns a magical 'Nothing' object which has
characteristics like - (->is_nothing === 1, ->id === 0, @list = $rs->method
=== (), $row = $rs->method === bless({}, Nothing). The result - no need to
if-then on empty resultsets when grabbing data.
</pre>
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<pre wrap=""><!---->
So, the following are different:
my $x = $rs->method;
my ($y) = $rs->method;
That's sucky.
</pre>
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interesting point. If I had the Want module, I could easily return
nothings if you have a specified number expected (1 in this case), or
empty list if you expect infinite - since ($y) = $rs->method is
different contextually than @y = $rs->method - which would make that
not sucky.<br>
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cite="mid:70384420903050917j69e76d90h70c10035719dae9d@mail.gmail.com"
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<blockquote type="cite">
<pre wrap="">I wanted to use the Want module to change the return considering the context
called in, but that module is, sadly, not compatible with mod_perl. If it
was, I could give back undefined, blessed ref, array ref, or hash ref
depending on its context, which would be cool. Dang segfaults...
</pre>
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<pre wrap="">Context-awareness, while cool, is kinda like operator overloading and
monkeypatching.</pre>
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Yes, it is. <br>
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cite="mid:70384420903050917j69e76d90h70c10035719dae9d@mail.gmail.com"
type="cite">
<pre wrap=""> It's something you should have in that section of your
toolbox that has the "Write 500 words as to why you should be allowed
to use me" essay requirement.
</pre>
</blockquote>
Well, in this case in order to cleanly express 'Nothing', which has
different meanings in different contexts, I need to be able to detect
that context so that I can be different for those contexts. Within the
limits of this particular design pattern, I think it is justifiable.
So though it is a bit sucky and constrains the implimentation patterns
(my $y = $rs->method SHOULD be equal to my ($y) = $rs->method),
but in my case the former is what you want) without the Want module...
I think that the pattern has good benefits in being able to cut down on
the if-then hooey. How I hate if-then/tertiaries/logical
operators/other repetitive code just to see if there's something there
to operate on.<br>
<br>
At least with AUTOLOAD handling miscellaneous calls, I don't have to
create special nothing hard-types one-to-parent-class as I would in
Java/C++ that behave appropriately. A nothing row that returns a
nothing date-object, etc.<br>
<br>
David<br>
<br>
<br>
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