Form For Association Comments on Posts

Question

I am trying to create comments that are associated with posts. There are 3 models User, microposts and Comments. Here are the associations that I have:
Comment Model

class Comment < ActiveRecord::Base
  belongs_to :user 
  belongs_to :micropost

  validates :user_id, presence: true
  validates :micropost_id, presence: true
end

Microposts Model

belongs_to :user
  has_many :comments, dependent: :destroy

User Model

has_many :microposts, dependent: :destroy
  has_many :comments

I have nested the route as:

resources :microposts do 
    resources :comments
  end

Here is my comment controller:

class CommentsController < ApplicationController

  def create
    @micropost = Micropost.find(params[:micropost_id])
    @comment = @micropost.comments.build(params[:comment])
    if @comment.save
      flash[:success] = "Comment created"
      redirect_to current_user
    else
      render 'shared/_comment_form'
    end
  end
end

Comment Form:

<%= form_for([@micropost, @comment]) do |f| %>
  <%= render 'shared/error_messages', object: f.object %>
  <div class="field">
    <%= f.text_area :content, placeholder: "Write your message.." %>
  </div>
  <%= f.submit "Post", class: "btn btn-primary" %>
<% end %>

When I run this I get a form I get an argument error,
First argument in form cannot contain nil or be empty
I am wondering how do I solve this issue? If I just write micropost, @comment it seems to not recognize it either and I get an undefined local variable error. Why is the comment form not realizing that the micropost is from the comments controller to find the micropost_id?

do yo you set the values of @micropost and @comment before this form ? — mohameddiaa27
render 'shared/_comment_form', micropost: @micropost. In your view change the global @micropost to local micropost. — Justin
I have done the micropost: @micropost but it still doesn't seem to be working Justin. I will get a undefined local local variable or name error... — Jason
mohammed, i have set the values of micropost in the comments controller as you can see as well as in the user controller which is @comment = comment.new — Jason

mohameddiaa27 mohameddiaa27 · Accepted Answer · 2014-11-03T18:29:29

Lets first understand how this form works.

If your resource has associations defined, for example, you want to add comments to the micropost given that the routes are set correctly:

<%= form_for([@micropost, @comment]) do |f| %>
 ...
<% end %>

Where @micropost and @comment are defined before rendering the form.

example: @micropost = Micropost.find(params[:id]) and @comment = Comment.new

Later when you submit this form (only on that step) your create action is touched from your comments controller.

so basically what you need to do, is define the @micropost and @comment before calling the form_for

Form For Association Comments on Posts

1 Answers