[Rails] map.resources with alternate primary key(s)

Question

I have a Rails model Object that does not have an ID column. It instead uses a tuple of primary keys from two other models as its primary key, dependency_id and user_id.

What I want to do is be able to do something like this in routes.rb:

map.resources :object, :primary_key => [:dependency_id, :user_id]

And for it to magically generate URLs like this:

/objects/:dependency_id/:user_id
/objects/:dependency_id/:user_id/1
/objects/:dependency_id/:user_id/1/edit

...Except that I just made that up, and there is no such syntax.

Is there a way to customize map.resources so I can get the RESTful URLs, without having to make custom routes for everything? Or am I just screwed for not following the ID convention?

The :path_prefix option looks somewhat promising, however I would still need a way to remove the id part of the URL. And I'd like to still be able to use the path helpers if possible.

Answer 1

You should override Object model's method to_param to reflect your primary key. Something like this:

def to_param
  [dependency_id, user_id].join('-')
end

Then when you'll be setting urls for these objects (like object_path(some_object)) it will automatically gets converted to something like /objects/5-3. Then in show action you'd have to split the params[:id] on dash and find object by dependency_id and user_id:

def show
  dep_id, u_id = params[:id].split('-').collect(&:to_i)
  object = Object.find_by_dependency_id_and_user_id(dep_id, u_id)
end

You can also look at find_by_param gem for rails.