<div dir="ltr">On Wed, Oct 1, 2008 at 7:06 PM, David Chelimsky <span dir="ltr"><<a href="mailto:dchelimsky@gmail.com" target="_blank">dchelimsky@gmail.com</a>></span> wrote:<br><div class="gmail_quote"><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div><br>
</div>Au contraire! You're comparing apples and cadillacs here. Demeter is<br>
about encapsulation. Interfaces are about abstraction and structure.<br>
Completely different animals.</blockquote><div><br>Interfaces in that Java book and LOD in this topic were being supported by arguments of the form "if you need to change things in the future..." There are some practitioners for whom that's a valid argument, and there are others for whom it's an anti-argument. YAGNI is the latter. Doesn't make it right, but it does provide a way to evaluate each of these animals.<br>
<br></div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Tracking down all of the trainwrecks in a system is not quite so<br>
simple. First of all, they are not guaranteed to look the same:<br>
<br>
trainer.animals.dogs.first<br>
<br>
vs<br>
<br>
t = trainer<br>
a = trainer.animals<br>
d = trainer.dogs<br>
dog = dogs[0]<br>
<br>
So when the design seems to want to categorize animals into domestic<br>
and wild, the first call has to be changed to<br>
trainer.animals.domestic.dogs.first. Good luck tracking down the<br>
second example</blockquote><div><br>In a statically-typed language, this would be trivial. In a dynamically-typed language using BDD, this would be caught by tests.<br> </div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Principles/guidelines like YAGNI and DRY and even the<br>
ever-threatening-sounding Law of Demeter are NOT LAWS. They are<br>
indicators. Red flag triggers. Red flags are *warnings*, not *errors*.<br>
</blockquote><div><br>We agree on that. See my recent post: <a href="http://www.nabble.com/Prepare-for-newbie-ness-to19516110.html#a19542377">http://www.nabble.com/Prepare-for-newbie-ness-to19516110.html#a19542377</a><br>
<br>In this case, we've got two of these in direct conflict with each<br>
</div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
other, so which one wins? Gotta look at the costs and benefits of each<br>
and proceed wisely and *in context*</blockquote><div><br>I feel that YAGNI and LOD are at different levels of granularity. I use YAGNI and TSTTCPW in my daily life (which isn't to say that I always think they're the best approach). So I approach problems using those principles as my base. I don't ask myself a hundred times a day whether I should use a goto statement - I use structured programming as my base. Same with OOP, readable code, lack of commenting, etc. You can't approach everything de novo. So I apply YAGNI unless I see a compelling reason not to. The reason is that the "costs and benefits" of any approach are usually not obvious - especially when talking about the future.<br>
<br>///ark<br></div></div></div>