Anyway for a model to call url_for?

Rails
1

Or better yet, a named route? Tried lots of searches and ugly hacks …

Thanks in advance.

2

Brittain wrote:

Or better yet, a named route? Tried lots of searches and ugly hacks …

If you want to do that, you’re probably trying to subvert MVC. There’s
no good way to do that and be happy using Rails. Usually there is a good
alternative, such as having the model construct a collection of simple
data items that the view or controller can use to create the URL. I did
that in my first Rails app, nothing to it.

–
Josh S.
http://blog.hasmanythrough.com

3

If you want to do that, you’re probably trying to subvert MVC. There’s
no good way to do that and be happy using Rails. Usually there is a good
alternative, such as having the model construct a collection of simple
data items that the view or controller can use to create the URL. I did
that in my first Rails app, nothing to it.

I ran into a similar dilemma a while back and I would appreciate it if
you would be more specific in a situation such as this:

You have a validate() method in a model and find an error. You call
errors.add() and realize that it is something that the user must
change on another page. Instead of writing “Ok, so if you look on the
right sidebar under the section heading ‘My Account’ click the blue
link ‘Settings’ and correct the discrepancy, then come back here and
try again” you could just write “Invalid account ___ (you can fix this
on your [link]User Settings[/url] page)”.

4

Josh S. <josh@…> writes:

Thanks for the response Josh. Since you’re with Rails Core can assume
there’s
no way to call url_for (or something equivalent) from a model then?

In the spirit of finding a more MVC way to handle this, here’s our
situation.
Feel free to provide a solution simpler than calling url_for:

We’ve a model object, Resource, that represents a web-accessible
resource in a
CMS. We also have a legacy system that tracks these same resources that
we’ve
built some Rails glue code to synchronize.

Our original design had a ResourceObserver that would update the legacy
system
after_save. However, the legacy system needs the fully-qualified URI.
Unfortunately, neither the model, nor observer can call url_for (or our
named
routes) to return the URI. (Although I suppose we could expose a
controller
method as a webservice that would return one for a given ID, but then
we’ve
exposed our primary key to another system…)

We considered storing the URI in the model object, but if our naming
changes
then we’ve persisted incorrect links and would prefer to have a method
URI that
would rewrite the URI whenever its needed. Particularly since that’s
consistent
with the semantics of our Resource model object.

Looking forward to hearing your ideas.

5

Brittain wrote:

Thanks for the response Josh. Since you’re with Rails Core can assume
there’s no way to call url_for (or something equivalent) from a model then?

Actually I’m not part of the core team. I’m just a blogger on the
official Rails blog. But even so I occasionally know what I’m talking
about :slight_smile:

We’ve a model object, Resource, that represents a web-accessible
resource in a CMS. We also have a legacy system that tracks these same
resources that we’ve built some Rails glue code to synchronize.

Our original design had a ResourceObserver that would update the
legacy system after_save. However, the legacy system needs the
fully-qualified URI. Unfortunately, neither the model, nor observer
can call url_for (or our named routes) to return the URI. (Although I
suppose we could expose a controller method as a webservice that would
return one for a given ID, but then we’ve exposed our primary key to
another system…)

We considered storing the URI in the model object, but if our
naming changes then we’ve persisted incorrect links and would
prefer to have a method URI that would rewrite the URI whenever its
needed. Particularly since that’s consistent with the semantics of our
Resource model object.

I think setting up the web service is the way to go. You don’t need to
expose the primary key to allow access to the Resource objects. You can
have the web service controller look up resources by name, date, UUID,
whatever… then generate a url for the resource in the controller. If
you think about it, the url only means something to the controller that
will be decoding it (with help of routes), so that controller is the
only agent qualified to construct it. That’s why models don’t know about
urls. That’s what’s behind the issue in your last paragraph.

–
Josh S.
http://blog.hasmanythrough.com

6

On Saturday, July 29, 2006, at 11:00 PM, Brittain wrote:

Or better yet, a named route? Tried lots of searches and ugly hacks …

Thanks in advance.

Rails mailing list
[email protected]
http://lists.rubyonrails.org/mailman/listinfo/rails

Then it’s probably time to ask… “If it’s this hard, should I be doing
it this way?”

In general, there is little need for models to know about things like
‘url_for’. url_for is generally used when you are rendering a view, so
that functionality should probably be in a controller or view.

Is there a compelling reason why you need to use this function from a
model?

_Kevin
www.sciwerks.com

7

Brittain wrote:

Or better yet, a named route? Tried lots of searches and ugly hacks …

Thanks in advance.

Hi! here’s one way to do it:

ActionController::Integration::Session.new.url_for(:host => “”,
:controller => “”, :action => “”)

cheers