Understanding associations in rails 3

Question

Seems I need to brush up on my associations in rails. At present I am trying to display all posts that have the department name as staff.

two models exist at present, posts and departments

class Post < ActiveRecord::Base
  belongs_to :department
  attr_accessible :title, :comments, :department_id
end

class Department < ActiveRecord::Base
  has_many :posts
  attr_accessible :name, :post_id
  #Scopes
  scope :staff_posts, where(:name => "Staff") 
end

So i want to display all posts that have the department name staff

to do this i have put this in my controller

class PublicPagesController < ApplicationController

  def staffnews
    @staffpost = Department.staff_posts
  end

end

In my view i am trying to display all these posts like so

<% @staffpost.each do |t| %>
  <h2><%= t.title %>
  <h2><%= t.comments %></h2>
<% end %>

Clearly going wrong somewhere as i get undefined method nil, even though i have 3 posts with the name 'Staff'

Can someone please explain where i am misunderstanding the association as would love to get this right

EDIT

Routes

scope :controller => :public_pages do 
get "our_news"

match "our_news/staffnews" => "public_pages#staffnews"

Answer 1

In controller it returns department with name staff. And you are using title and comments on on department objects thats why its giving nil method error.

Use like this:

 def staffnews
   @dept_staff = Department.staff_posts
 end

 <% @dept_staff.each do |ds| %>
   <% ds.posts.each do |p| %>
     <h2><%= p.title %></h2>
     <h2><%= p.comments %></h2>
   <% end %>
 <% end %>

or

In post model create named_scope

class Post < ActiveRecord::Base
  belongs_to :department
  attr_accessible :title, :comments, :department_id
  scope :staff_posts, :include => :department, :conditions => {"departments.name" => "Staff"}
end


class Department < ActiveRecord::Base
  has_many :posts
  attr_accessible :name, :post_id
end

Controller:

def staffnews
  @staffpost = Post.staff_posts
end

View: #No change

<% @staffpost.each do |t| %>
  <h2><%= t.title %></h2>
  <h2><%= t.comments %></h2>
<% end %>