[Catalyst] Model Instances vs. Model Classes - Round 2

[Alejandro Imass]

Hi,

As a few may remember I brought this up a while ago and after working
with this for a while I just want to make sure we are really
understanding and using this correctly...

Postulates:
1) Ideally all the business code should be abstracted into models and
more ideally these models should be classes that are independent from
Catalyst. We shall call these business model classes to differentiate
them from Catalyst Model classes.
2) The Catalyst model as such (script/xx_create.pl model yyy) should
be a thin wrapper to the business model classes from postulate 1.
3) Catalyst Models may be classes or instances.

Design Patterns:
1) If the Catalyst model will be a class, the pattern is very simple:
The catalyst model class uses the business object class just like any
other library. As I understand it, the controller code would have to
invoke new() on the model class to create a new instance of the class
that will die with the request (will lose scope from the controller
method that created it).
2) If the Catalyst model will be an instance, the design pattern is a
per-request object factory. The fat code should be kept in the
instance class, and the ACCEPT_CONTEXT method should be used to
instantiate a leaner class and return _that_ to the controller. The
idea of an instance, is that most of the heavy duty code remain
instantiated and the code is purely functional.

Assumptions and Questions
1) Is the assumption that in the first design pattern the controller
has to call new() correct? (I have always worked with the second
pattern, so I don't know for sure).
2) For Catalyst instance models, the request classes should not
contain any heavy duty code. So forcibly the request class needs a
reference to the parent model class (the factory). This is so the
request class is able to use the methods of the factory class. Is this
assumption correct?
3) It is written somewhere (I couldn't find it before writing this but
I know is in the POD somewhere) that it is not a good idea to pass the
complete $c reference to the per-request object, but rather only the
necessary pieces of $c. What are the implications of passing the
complete $c ?

Any other comments greatly appreciated. I think this could make an
interesting article for the Wiki so I want to get all the real experts
opinions on this before I attempt to create it.

Thanks,

--
Alejandro Imass