Redirecting from polymorphic association - ruby-on-rails

Question

I have a comments model that belongs to two models: submissions and posts
class Comment < ActiveRecord::Base
attr_accessible :content, :show
belongs_to :commentable, :polymorphic => true
end
class Submission < ActiveRecord::Base
has_many :comments, :as => :commentable, :dependent => :destroy
end
Submissions is a nested route and post is not.
In my comments controller:
def create
#commentable = find_commentable
#comment = #commentable.comments.build(params[:comment])
#comment.user = current_user
if #comment.save
#CommentMailer.comment_email(#user, #comment, #commentable).deliver
flash[:notice] = "Successfully created comment."
if #commentable == #submission
redirect_to [#contest, #commentable]
else
redirect_to [#commentable]
end
else
render :action => 'new'
end
end
find_contest
def find_contest
#contest = Contest.find(params[:contest_id])
end
find_commentable:
def find_commentable
params.each do |name, value|
if name =~ /(.+)_id$/
return $1.classify.constantize.find(value)
end
end
nil
end
The redirect to post via #commentable works fine, but the redirect to submissions is not finding the contest.
Started POST "/submissions/36/comments" for 127.0.0.1 at 2012-11-30 18:34:41 -0800
Processing by CommentsController#create as HTML
Parameters: {"utf8"=>"✓", "authenticity_token"=>"R62NH5/EE34FPapEqy7mfpa0wKz18GtSdhH8MGYq2Ec=", "comment"=>{"content"=>"test", "show"=>"true"}, "commit"=>"Create Comment", "submission_id"=>"36"}
User Load (0.4ms) SELECT "users".* FROM "users" WHERE "users"."id" = 2 ORDER BY users.created_at DESC LIMIT 1
Submission Load (0.3ms) SELECT "submissions".* FROM "submissions" WHERE "submissions"."id" = $1 ORDER BY submissions.created_at DESC LIMIT 1 [["id", "36"]]
Completed 500 Internal Server Error in 116ms
ActiveRecord::RecordNotFound (Couldn't find Contest without an ID):
app/controllers/comments_controller.rb:19:in `create'
Change to submission routes:
submissions GET /submissions(.:format) submissions#index
POST /submissions(.:format) submissions#create
new_submission GET /submissions/new(.:format) submissions#new
edit_submission GET /submissions/:id/edit(.:format) submissions#edit
submission GET /submissions/:id(.:format) submissions#show
PUT /submissions/:id(.:format) submissions#update
DELETE /submissions/:id(.:format) submissions#destroy
Submission form:
<%= simple_form_for #submission, :html => { :multipart => true } do |f| %>
<div class="span7 offset2 submission">
<fieldset class="well pleft80 edit">
<%= f.hidden_field :contest_id , :value => params[:contest_id] %>
<%= f.input :title %>
<%= f.input :description %>
<%= f.input :comment_show, :as => :hidden, :input_html => { :value => true } %>
</fieldset>
<fieldset class="well pleft80 noborder">
<%= f.fields_for :image do |img_field| %>
<h3>Upload Photo<%= img_field.file_field :source %></h3>
<% end %>
</fieldset>
<div class ="form-actions pleft80">
<%= f.submit nil, :class => 'btn btn-primary btn-large' %>
</div>
</div>
<% end %>

Answer 1

You don't need to instantiate or classify anything.
redirect_to #comment.commentable
If you can't do that then you will need to build a global helper module for it and include that into the controller.
module RouteHelpers
def comment_association_redirect_to(comment)
item = comment.commentable
case item.class.to_s
when 'Submission'
redirect_to submission_path(item)
end
end
end
And include it within the ApplicationController:
include RouteHelpers
Then you can call comment_association_redirect_to anywhere in your app (controllers and so on).

Answer 2

I stripped the nested routing out of the app and now it works fine and it's much simpler. Not sure I can think of a good reason to use nested routing when the views must relate the dependencies.