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From: Vitaly Kushner <vit...@astrails.com>
Date: Tue, 15 Jun 2010 01:30:51 +0300
Message-ID: <AANLkTimT6M0WWbITpcMj3DzsGBciJETUYvdzZph0f...@mail.gmail.com>
Subject: Re: session variable and model code
To: israelrb@googlegroups.com
Content-Type: text/plain; charset=UTF-8

On Tue, Jun 15, 2010 at 12:54 AM, Dor Kalev <d...@dorkalev.com> wrote:
> MVC is a great framework! Elad, I think what you are really looking for is a
> religion ;-)
+1

> On Tue, Jun 15, 2010 at 12:02 AM, Elad Meidar <eize....@gmail.com> wrote:
>>
>> I just vomited a little bit in my mouth ;)

Indeed dogma is never right. You always have exceptions. An
inexperienced craftsman is better be following the strictest rules for
the purpose of not hurting himself. But with time you acquire enough
knowledge to see beyond the rules and dogmas and to bend the rules
when needed in a careful and elegant way.

Several use-cases I had (all so far required url helpers in the model).

==== 1

*  existing rails site. clean code. restful and a lot of
inherited_resources use.
* requirement: add an .xml api with minimal effort
* some xml responses need to include urls of other xml resources (this
is required by the *proper* rest api)
  i.e. resource /users.xml doesn't just list user ids, but as is
required by the properly designed rest it includes direct urls to user
resources.

the most natural way to implement something like this in Rails is to
just use model.to_xml or collection.to_xml. the only thing that needs
to be
done then is to override as_json funciton in the models where you
don't want to expose the whole internal structure or need special
handling (like the urls)

problem: you can't construct urls in the model.

simplest possible solution: give models access to controller's url helpers.

And don't bring me this 'you  break MVC' bullshit, because it is just
that : bullshit ;)
by your logic I18n breaks MVC too because it saves current locale in a
global variable.

the thing is, some stuff in the 'current request context' can be
required all over the place. one example is current_locale, another is
current_anything_that_knows_to_construct_urs_using_the_right_host_and_port_and_routes.
in case of I18n they had a clear place to stick their global into as
they had a separate module for it. but it still breaks the frigging
MVC.

in our case I couldn't care less for the purity of MVC and exposing
the current_controller for the purpose of
current_controller.user_path(user) was the right thing to do.

==== 2
There is another use case. I had it on one of our first projects and
at the time it was solved by some other hack I don't even remember
now, but if I were to implement it today I would definitely use
current_controller.
We needed to implement db backed html widgets. there were several
kinds and they were implemented with single-table-inheritance over a
single table.
Again, from the usage pattern of it it made a lot of sense to just
have widget.to_html. This use case is arguably less demanding to break
the MVC since there *is* a fairly easy workaround (pass current view.
i.e. you'd do <%= @widget.to_html(self) %> in your views, but it also
looks and feels quite kludgy


You can read my old blog post about it
http://blog.astrails.com/2009/10/27/liberate-my-controller

--
Vitaly Kushner
http://twitter.com/vkushner
Founder, Astrails Ltd. http://astrails.com/
Check out our blog: http://blog.astrails.com/