如何在Rails中使模型知道其控制器？

Question

I am making a Rails application, and i would like to be able use a model object passed to a view to get the URL of some action on this object, like this, for example:

link_to object.public_send(attribute),
        { :controller => object.controller_path,
          :action     => :show,
          :id         => object.id }

What would be a good way to do this? Can it be done with a decorator like Draper ? Are there some examples online?

---

Update. I have thought about this and decided that a decorator is not a good place to keep controller information. It is not decorator's responsibility. A decorator should only know to render formatted data with markup. For now i have created a module called Accessor where i try to mix models with controller and routing awareness. I still wonder if there is a better way to do.

Answer 1

If you don't mind having another instance variable on your view, you can implement this using a very simple class (no need for decorators).

class MyRouter
  def initialize(controller, object)
    @controller = controller
    @object     = object
  end

  def url_for(action_name)
    controller.url_for(object, :action => action_name)
  end
end

On your controllers:

class AController
  def edit
    @router = MyRouter.new(self, object)
    render 'shared_view'
  end
end

class BController
  def edit
    @router = MyRouter.new(self, object)
    render 'shared_view'
  end
end

And on your shared view:

<%= @router.url_for(:show) # Varies with the controller that rendered the view %>

Of course, this assumes that the controller you want as target is the same controller that renders the view, which might not be true. Still, using this pattern you can accommodate a more complex logic that suits your needs (having multiple Router classes, for instance), without having to change the view.

Answer 2

I've found a very interesting solution in Objects on Rails by Avdi Grimm: Exhibits for REST . In short, his idea is to apply multiple Ruby's SimpleDelegator s as decorators with various functions.