has_many :through issue

gistfile1.rb

class User < ActiveRecord::Base
  attr_accessible :email, :password, :password_confirmation, :remember_me, :username, :profile_image, :first_name, :last_name
  has_many :publications
	has_many :threads, :through => :publications
end

class Publication < ActiveRecord::Base
  attr_accessible :thread_id, :user_id
  belongs_to :thread
  belongs_to :user
  accepts_nested_attributes_for :thread
end

class Thread < ActiveRecord::Base
  attr_accessible :description, :name, :tag_list, :thumbnail_image, :status, :thread_type, :subtitle, :summary
  has_one :publication
  has_one :user, :through => :publication
end

# Begin form for creating new thread
= form_for [@user, @thread] do |f|
  - if @thread.errors.any?
    #error_explanation
      %h2= "#{pluralize(@thread.errors.count, "error")} prohibited this thread from being saved:"
      %ul
        - @thread.errors.full_messages.each do |msg|
          %li= msg

  .field
    %span Title:
    = f.text_field :name

  .actions
    = f.submit 'Submit'