ActionController::UrlGenerationError in Comments#edit - Rails 4.0 - ruby-on-rails

Question

I am using a ruby on rails blog tutorial and everytime I try to edit a comment I get an error.
Error: No route matches missing required keys: [:id].
Please help I am new to this.
Error found around line 3.
<h1>Editing comment</h1>
3. <%= form_for([:post, #comment]) do |f| %>
4. <div class="field">
5. <%= f.label :name %>
<%= f.text_field :name %>
Here is my routes.rb file code
Rails.application.routes.draw do
resources :posts do
resources :comments
end
end
My Comments_controller.rb code
class CommentsController < ApplicationController
# GET /comments
# GET /comments.json
def index
#comments = Comment.all
respond_to do |format|
format.html # index.html.erb
format.json { render json: #comments }
end
end
# GET /comments/1
# GET /comments/1.json
def show
#comment = Comment.find(params[:id])
respond_to do |format|
format.html # show.html.erb
format.json { render json: #comment }
end
end
# GET /comments/new
# GET /comments/new.json
def new
#comment = Comment.new
respond_to do |format|
format.html # new.html.erb
format.json { render json: #comment }
end
end
# GET /comments/1/edit
def edit
#comment = Comment.find(params[:id])
end
# POST /comments
# POST /comments.json
def create
#post = Post.find(params[:post_id])
#comment = #post.comments.build(comment_params)
respond_to do |format|
if #comment.save
format.html { redirect_to #post, notice: 'Comment was successfully created.' }
format.json { render json: #post, status: :created, location: #comment }
else
format.html { render action: "new" }
format.json { render json: #post.errors, status: :unprocessable_entity }
end
end
end
# PUT /comments/1
# PUT /comments/1.json
def update
#comment = Comment.find(params[:id])
#post = #comment.post
respond_to do |format|
if #comment.update_attributes(params[:comment])
format.html { redirect_to #post, notice: 'Comment was successfully updated.' }
format.json { head :no_content }
else
format.html { render action: "edit" }
format.json { render json: #post.errors, status: :unprocessable_entity }
end
end
end
# DELETE /comments/1
# DELETE /comments/1.json
def destroy
#comment = Comment.find(params[:id])
#post = Post.find(params[:post_id])
#comment.destroy
respond_to do |format|
format.html { redirect_to #post, notice: 'Comment was successfully deleted!' }
format.json { head :no_content }
end
end
def comment_params
params.require(:comment).permit(:post_id, :name, :email, :body)
end
end

Answer 1

So, to leave the comments alone, let me try to explain what I think it is your problem.
In your routes file you have nested resources, which means that this:
resources :posts do
resources :comments
end
end
are what is called nested resources, and this means that you have routes like:
posts/:post_id
posts/:post_id/comments/:comment_id
which you can see if you run rake routes.
This also means that the first route will call an action on your PostsController and the second route will call an action on your CommentsController.
So what I suggested you to do in your controller was to, first, render the form as [#post, #comment], which will tell the form_for helper to use your nested resource as the 'path to send the form'.
For this form to call your edit method you'll need to say that you want the form to be submitted there. This is done by the options for the form_for helper (http://api.rubyonrails.org/classes/ActionView/Helpers/FormHelper.html) and this is necessary because rails loves/is! RESTfull, and under this, the same route might have multiple behaviours depending on the HTTP verb/method you use.
So, have attention to this that I mentioned above, and you can probably guess what you are doing wrong.
As a last hint, your controller has this:
# GET /comments/1/edit
def edit
#comment = Comment.find(params[:id])
end
And this method renders this(I assume):
<h1>Editing comment</h1>
<%# I already fixed the form_for here %>
<%= form_for([#post, #comment]) do |f| %>
<div class="field">
<%= f.label :name %>
<%= f.text_field :name %>
<% end %>
This form, since is rendered by the edit action, will (probably) be submitted to the update action. This update action is under /posts/:post_id/comments/:comment_id, and can be called using the PATCH(rails 4.0) verb. So your form_for needs, first, to have a post assigned to the variable #post, which should be passed by its controller. Second, it needs to go to the right route.
Here you are lucky since Rails is smart enough to see if what you're submitting is a new_record? and then its form_for will point to create or, if not, will point to update.
So all you need to do now, is to assign the right Post to #post and you are probably good to go.
Let me know if this worked for you.