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copied!<p>It's kind of difficult to wrap your head around it because you don't know what kind of object you're going to be receiving in the comments controller.</p> <p>It's much simpler when it's not a polymorphic relationship. Before we understand how to do that, we need to understand the best way to do the singular version.</p> <p>I should note that this assumes that you have your resources/routes defined correctly:</p> <p>map.resources :posts, :has_many => [ :comments ] map.resources :pages, :has_many => [ :comments ]</p> <p>Let's say that we have the simple example of a Post has many Comments. Here is a sample way of doing this:</p> <pre><code>class CommentsController < ApplicationController before_filter => :fetch_post def create @comment = @post.comments.new(params[:comment]) if @comment.save success_message_here redirect post_path(@post) else error_message_here redirect_to post_path(@post) end end protected def fetch_post @post = Post.find(params[:post_id]) end end </code></pre> <p>Now we want to use this in a polymorphic relationship, so we have to setup a couple of things. Let's say that we have Pages and Posts that have comments now. Here is a sample way of doing this:</p> <p>From you Posts and Pages show pages:</p> <pre><code><%= render 'comments/new' %> </code></pre> <p>In the posts controller:</p> <pre><code>before_filter :fetch_post def show @comment = @commentable.comments.build end protected def fetch_post @post = @commentable = Post.find(params[:id]) end </code></pre> <p>This sets up your form to be simple: <% error_messsages_for :comment %></p> <pre><code><% form_for [ @commentable, @comment ] do |f| %> #Your form fields here (DO NOT include commentable_type and or commentable_id also don't include editor and creator id's here either. They will created in the controller.) <% end %> </code></pre> <p>In your comments controller:</p> <pre><code>def create @commentable = find_commentable # Not sure what the relationship between the base parent and the creator and editor are so I'm going to merge in params in a hacky way @comment = @commentable.comments.build(params[:comment]).merge({:creator => current_user, :editor => current_user}) if @comment.save success message here redirect_to url_for(@commentable) else failure message here render :controller => @commentable.class.downcase.pluralize, :action => :show end end protected def find_commentable params.each do |name, value| if name =~ /(.+)_id$/ return $1.classify.constantize.find(value) end end nil end </code></pre>

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