## create_cases.rb
class CreateCases < ActiveRecord::Migration
  def self.up
    create_table :cases do |t|
...
    end

	create_table :cases_users, :id => false do |t|
		t.column :case_id, :integer
		t.column :user_id, :integer
	end

	add_index :cases_users, [:case_id, :user_id]
	add_index :cases_users, [:user_id, :case_id]
  end

  def self.down
    drop_table :cases
  end
end

## cases_controller.rb
  def add
	@case = Case.find(params[:id])
	@user = User.find(session[:user].id)
	@case << @user

	redirect_to :controller => :cases, :action => :my_cases
  end

## user.rb
require 'digest/sha1'

class User < ActiveRecord::Base
  include Authentication
  include Authentication::ByCookieToken

  has_and_belongs_to_many :cases
....
end

## case.rb
class Case < ActiveRecord::Base
	has_and_belongs_to_many :users
...
end

## error
NoMethodError in CasesController#add

undefined method `<<' for #<Case:0xb6a24a84>
RAILS_ROOT: /home/tim/Code/unclaimed

Application Trace | Framework Trace | Full Trace
vendor/rails/activerecord/lib/active_record/attribute_methods.rb:256:in `method_missing'
app/controllers/cases_controller.rb:35:in `add'
/var/lib/gems/1.8/gems/mongrel-1.1.5/lib/mongrel/rails.rb:76:in `process'
/var/lib/gems/1.8/gems/mongrel-1.1.5/lib/mongrel/rails.rb:74:in `synchronize'
/var/lib/gems/1.8/gems/mongrel-1.1.5/lib/mongrel/rails.rb:74:in `process'
/var/lib/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:159:in `process_client'
/var/lib/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:158:in `each'
/var/lib/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:158:in `process_client'
/var/lib/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:285:in `run'
/var/lib/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:285:in `initialize'
/var/lib/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:285:in `new'
/var/lib/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:285:in `run'
/var/lib/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:268:in `initialize'
/var/lib/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:268:in `new'
/var/lib/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:268:in `run'
/var/lib/gems/1.8/gems/mongrel-1.1.5/lib/mongrel/configurator.rb:282:in `run'
/var/lib/gems/1.8/gems/mongrel-1.1.5/lib/mongrel/configurator.rb:281:in `each'
/var/lib/gems/1.8/gems/mongrel-1.1.5/lib/mongrel/configurator.rb:281:in `run'
/var/lib/gems/1.8/gems/mongrel-1.1.5/bin/mongrel_rails:128:in `run'
/var/lib/gems/1.8/gems/mongrel-1.1.5/lib/mongrel/command.rb:212:in `run'
/var/lib/gems/1.8/gems/mongrel-1.1.5/bin/mongrel_rails:281
Request

Parameters:

{"id"=>"1091"}
Show session dump

Response

Headers:

{"cookie"=>[],
 "Cache-Control"=>"no-cache"}