ActionController::UrlGenerationError in Comments#show

Question

I use polymorphic associations with comments. When I try to add 'edit' and also 'destroy' in show template, I get the error in the title (just edit for now). How do I add both links to show?

comments_controller.rb

class CommentsController < ApplicationController
  ....
  before_action :signed_in_user, only: [:new, :edit]
  before_filter :load_commentable

def index
  @commentable = load_commentable
  @comments = @commentable.comments
end

def show
end

def edit
  @commentable = load_commentable
end

def new
 @commentable = load_commentable
 @comment = @commentable.comments.new
end

def create
 @comment = @commentable.comments.new(comment_params)
 @comment.user = current_user

if @comment.save
  redirect_to @comment, notice: "Created."
 else
  render :new
 end
end

def update
  @comment = @commentable.comments.build(comment_params)
  @comment.user = current_user

respond_to do |format|
  if @comment.update(comment_params)
    format.html { redirect_to @comment, notice: 'It was successfully updated.' }
    format.json { head :no_content }
  else
    format.html { render action: 'edit' }
    format.json { render json: @comment.errors, status: :unprocessable_entity }
  end
 end
end



private

def load_commentable
  resource, id = request.path.split('/')[1, 2]
  @commentable = resource.singularize.classify.constantize.find(id)
end

....

end

show.html.erb template

<%= link_to "Edit", [:edit, @commentable, :comment] %>

form

<%= form_for [@commentable, @comment] do |f| %>
....

full trace

log

Processing by CommentsController#show as HTML
Parameters: {"post_id"=>"1", "id"=>"2"}
Comment Load (0.3ms) SELECT "comments".* FROM "comments" WHERE "comments"."id" = ? LIMIT 1 [["id", "2"]]
Post Load (0.2ms) SELECT "posts".* FROM "posts" WHERE "posts"."id" = ? LIMIT 1 [["id", "1"]]
User Load (0.2ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? ORDER BY "users"."id" ASC LIMIT 1 [["id", 2]]
(0.2ms) SELECT COUNT(*) FROM "comments" WHERE "comments"."user_id" = ? [["user_id", 2]] CACHE (0.0ms) SELECT COUNT(*) FROM "comments" WHERE "comments"."user_id" = ? [["user_id", 2]]
Rendered comments/show.html.erb within layouts/application (10.7ms)
Completed 500 Internal Server Error in 19ms

ActionView::Template::Error (No route matches {:action=>"edit", :controller=>"comments", :post_id=>#, :id=>nil, :format=>nil} missing required keys: [:id]):

25:           <div class="thumbsdown"><%= link_to image_tag('othericons/thumbiconDown.PNG', height: '20', width: '20'),

"#" %>
26: <%= link_to image_tag('othericons/flagicon.PNG', height: '20', width: '18'), "#" %>
27:
28: <%= link_to "Edit", [:edit, @commentable, :comment] %> 29:
30:

31: app/views/comments/show.html.erb:28:in `_app_views_comments_show_html_erb___2937579164590753686_69833853514120'

Rendered /home/action/.rvm/gems/ruby-2.0.0-p247/gems/actionpack-4.0.0/lib/action_dispatch/middleware/templates/rescues/_trace.erb

(1.6ms) Rendered /home/action/.rvm/gems/ruby-2.0.0-p247/gems/actionpack-4.0.0/lib/action_dispatch/middleware/templates/rescues/_request_and_response.erb (1.2ms) Rendered /home/action/.rvm/gems/ruby-2.0.0-p247/gems/actionpack-4.0.0/lib/action_dispatch/middleware/templates/rescues/template_error.erb within rescues/layout (19.1ms)

routes:

resources :posts do
  resources :comments
end

Answer 1

Change the Edit Link as below:

<%= link_to "Edit", edit_post_comment_path(@commentable, @comment) %> 

You have setup Post and Comment as nested routes, so you need to pass objects of Post as well as Comment to the edit path.

EDIT

For Polymorphic association, you could use it as below:

<%= link_to "Edit", [:edit, @commentable, @comment] %>