Question

Disclaimer: first month of developing with rails, but I have read everything I could find.

Edit: Somehow I missed this very similar question with a similar final answer.

I have polymorphic flags:

Class Flag...
  belongs_to :flaggable, :polymorphic => true
  ...
end

I have nested resources that have the appropriate has_many :flags, :as => :flaggable statement.

resources :posts do
  resources :comments
end

I would like both posts and comments and in the future other things on the site to be flaggable. What is the DRY/standard way (I’m using Rails 3.1) to do this with regard to routes and controller?

---

What I did for routes:

Mostly based on this rails cast, I made flags as a nested resource of both posts and comments. Already, I think I’m on the wrong track because it seems to be re-stating the polymorphic relationships in the models as well as breaking the guideline that “Resources should never be nested more than 1 level deep.”

resources :posts do
  resources :flags
  resources :comments do
    resources :flags
  end
end

Alternatively, I thought to implement the flaggable routes separately as below. But again, this doesn’t seem DRY and additionally makes non-desired independent routes for comments.

resources :posts do
  resources :flags
end
resources :comments do
  resources :flags
end

Finally, I wondered if I could make a generic resource for flaggables. I couldn’t find any way to implement this and it has the same problem of the previous method of making general routes available for the generic flaggable type.

resources :flaggable do
  resources :flags
end

---

What I did for the controller for the nested resources above:

I implemented find_flaggable, but realized that with nested resources, the parameter that gets converted to a flaggable class could be either Post or Comment since both end up in parameters (post_id and comment_id). I could solve the below with an id priority list for the current setup, but that is not a general solution and makes it even less DRY than it already is.

def find_flaggable
  params.each do |name, value|
    if name =~ /(.+)_id$/
      return $1.classify.constantize.find(value)
    end
  end
  nil
end

---

So this is where I stopped (actually implemented a limited solution only for Posts and Comments) and realized I don’t know a satisfying way to accomplish this. Can anyone help?

Answer 1

Just to solve the bit of DRYing up the code in your routes, a simple way would be to use

[:posts, :comments, :yet_another_resource].each do |resource_type|
  resources resource_type do
    resources :flags
  end
end

instead of

resources :posts do
  resources :flags
end
resources :comments do
  resources :flags
end

This starts becoming really clean and useful when you have a lot of actions under your nested resources. Sort of like a simple version of the “Extract method” refactoring for your routes.

EDIT

In case you missed my comment, I think polymorphic_url is the right thing you are looking for!!