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Re: Language wars...
- Subject: Re: Language wars...
- From: Ed W <..hidden..>
- Date: Thu, 25 Jan 2007 11:03:04 +0000
You are correct, you don't have to use the ORM and you can break out of
it. But then why use it at all? It is reasonably simple (especially the
direction we are going) to just have a sane api that you don't have to
break out of.
Well, my point was that it's not really "breaking out". The Model bit
of MVC just means package up the data access part and seperate it from
the controller code. It's a conceptual thing, not something to break
out of. Catalyst doesn't appear to particularly bind you to use a
database (as far as I can see, although it's true that Rails does to a
Why use it at all? Well because the framework does soooo much more than
just give you database access. The whole point is to provide the whole
framework for free and you only need to write small amounts of custom code.
Consider that the code for say, viewing a transaction becomes just
Bunch of SP's to load the data
TT code to display the transaction
Load different transactions, check we get the right stuff
Call render, check it displays some sensible data
Check we can click the edit, delete, print buttons without error, etc
Check we can't view the transaction without being logged in
Notice how easy it is to chuck in a bunch of test code which does unit
testing of the model and also checks that all the controller code still
It really is very neat once you manage to get a complete MVC
separation. In the case of a financial app with lots of business logic
it's extra nice because it helps focus people's mind on getting the
business rules correct first and rendering the stuff second. It's quite
a lot easier to just write a test app which manipulates the database and
arses around with it trying to break it. You just instantiate a couple
of models, start calling functions on them, then check that the database
still looks consistent - great for testing
Actually in Rails there is a bit of a backdoor here and there is a
"console" application provided. This makes it very easy to do database
maintenance by simply dropping into the console, typing
...then pick out a transaction, and start manipulating it:
a = Customer.find_by_name("bob").transactions(1)
b = Customer.find_by_name("Kate").transactions.new
See how easy it is to get an interface into your code once you go down
In the latest Rails they added a neat twist and let you call a different
render template based on how the request was phrased. So you basically
prepare all the data for an invoice, then you can have the output in XML
*or* HTML (or PDF, or PS, etc, etc). The addition of an XML input
parser came next and now you can post to the "edit" action in *either*
XML *or* HTML Form! This tiny bit of extra framework means that you can
now very easily keep 95% the same code and yet largely support a REST
interface to your whole application with very little code to change!
Wow - cool.
This is the power of separating the framework from the application in my
opinion. So really it should be written FMVC, and the code separated
But to be clear, I am NOT advocating that SMB needs use Catalyst. I
just want to re-iterate that if you haven't at least written a short
test application in one of the new MVC frameworks then you really are
missing out on a lot of good *ideas*. It really doesn't matter (that
much) whether it's Django, Catalyst, Rails, or whatever...
Good luck all