Re: Language wars...

[Ed W <..hidden..>]

Hi

> 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 
certain degree).

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

Controller:
   model.load(transaction_id)
   render

Model:
   Bunch of SP's to load the data

View:
   TT code to display the transaction

Test:
   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
   etc


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 
works!

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

Customer.find_by_name("bob").transactions

...then pick out a transaction, and start manipulating it:

a = Customer.find_by_name("bob").transactions(1)
print a.tax
print a.shipping_address

b = Customer.find_by_name("Kate").transactions.new
b.line_item.add(....)
b.save

See how easy it is to get an interface into your code once you go down 
this route?!

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 
accordingly



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

Ed W