Setting a comment form on a post - ruby-on-rails

Question

I would like to set a comment form on a post in the "group message show" view.But I have an error message like,
NoMethodError at /group_messages/64
undefined method `group_message_group_message_comments_path' for #<#:0x007f9c0afa0b38>
Could you give me some advice?
☆show.html.erb(group_messages)
<h2>Add a comment</h2>
<%= form_for([#group_message, #group_message_comment]) do |f| %>
<% if #group_message_comment.errors.any? %>
<div id="error_explanation">
<h2><%= pluralize(#group_message_comment.errors.count, "error") %> prohibited this group_message_comment from being saved:</h2>
<ul>
<% #group_message_comment.errors.full_messages.each do |msg| %>
<li><%= msg %></li>
<% end %><%# do%>
</ul>
</div><!-- error_explanation-->
<% end %><%# if any?%>
<div class="field">
<%= f.label :member_id %><br />
<%= f.number_field :member_id %>
</div>
<div class="field">
<%= f.label :gmessage_id %><br />
<%= f.number_field :group_message_id %>
</div>
<div class="field">
<%= f.label :group_id %><br />
<%= f.number_field :group_id %>
</div>
<div class="field">
<%= f.label :content %><br />
<%= f.text_field :content %>
</div>
<div class="actions" >
<%= f.submit "Comment"%>
</div>
<% end %><%# form_for>
☆group_messages_controller
def show
if !checklogin? then return end
#group_message = GroupMessage.find(params[:id])
#isme = me? #group_message
#group_message_comment = GroupMessageComment.new
#group_message_comment = GroupMessage.find(params[:id]).group_message_comments.build
respond_to do |format|
format.html # show.html.erb
format.json { render json: #group_message }
end
end
☆GroupMessage model
class GroupMessage < ActiveRecord::Base
attr_accessible :content, :member_id, :group_id
belongs_to :member
belongs_to :group
has_many :group_message_comments
end
☆GroupMessageComment model
class GroupMessageComment < ActiveRecord::Base
attr_accessible :content, :gmessage_id, :group_id, :member_id
belongs_to :member
belongs_to :group_message
end
☆routes.rb
MiniSNS::Application.routes.draw do
resources :group_message_comments
root :to => 'members#login'
match '/groups/join'
resources :group_messages
resources :groups do
resources :group_messages
end
match '/members/new'
resources :index
resources :groups
post 'groups/:id' => 'group#show'
post '/groups/new'
post '/index/index'
match '/members/login'
match '/members/logout'
match '/members/friend'
match 'members/show'
post 'messages/comment'
resources :comments
resources :messages
resources :friends
resources :members

Answer 1

That error message is due to the following line of code:
<%= form_for([#group_message, #group_message_comment]) do |f| %>
This is because you haven't set the correct routing for your models. Can you post your routes.rb too so that I can have a look?
I think you need nested routes, something like:
resources :group_messages do
resources :group_message_comment
end