Need help figuring out submitting a form for polymorphic models from associated controller

comment.rb

# models/comment.rb
class Comment < ActiveRecord::Base
  belongs_to :commentable, polymorphic: true
  validates :name, presence: true
end

comments_controller.rb

class CommentsController < ApplicationController
  def create
    @post = Post.find(params[:post_id])
    @comment = @post.comments.new comment_params
    @comment.status = 'pending'

    respond_to do |format|
      if @comment.save
        format.html { redirect_to @post, notice: 'Comment was successfully created.' }
        format.json { render action: 'show', status: :created, location: @comment }
      else
        format.html do
          flash[:notice] = "Error creating comment: #{@comment.errors}"
          redirect_to @post
        end
        format.json { render json: @comment.errors, status: :unprocessable_entity }
      end
    end
  end
end

post.rb

# models/post.rb
class Post < ActiveRecord::Base

  VALID_STATUSES = %w(draft published trash)

  validates :status, inclusion: VALID_STATUSES
  validates :title, :body, presence: true

  has_many :comments, as: :commentable, dependent: :destroy
end

show.html.erb

<%# posts/show.html.erb %>
<p id="notice"><%= notice %></p>

<p>
  <strong>Title:</strong>
  <%= @post.title %>
</p>

<p>
  <strong>Body:</strong>
  <%= @post.body %>
</p>

<p>
  <strong>Status:</strong>
  <%= @post.status %>
</p>

<hr />

<h2>Comments</h2>
<% @post.comments.each do |comment| %>
    <div class="comment" style="border-bottom: 1px dotted grey">
    <p>
      <strong>Name:</strong>
      <%= comment.name %>
    </p>

    <p>
      <strong>Comment:</strong>
      <%= comment.comment %>
    </p>
    </div>
<% end %>

<h2>Add a comment:</h2>
<%= form_for([@post, @post.comments.build]) do |f| %>

    <p>
      <%= f.label :name %><br />
      <%= f.text_field :name %>
    </p>
    <p>
      <%= f.label :email %><br />
      <%= f.text_field :email %>
    </p>
    <p>
      <%= f.label :comment %><br />
      <%= f.text_area :comment %>
    </p>
    <p>
      <%= f.submit %>
    </p>
<% end %>

<%= link_to 'Edit', edit_post_path(@post) %> |
<%= link_to 'Back', posts_path %>