Naming error in controller

I get this error when trying to create a record in my joins table

NameError in SubscriptionsController#new

uninitialized constant Channel::ChannelsUser

Subscriptions Controller

class SubscriptionsController < ApplicationController

  helper_method :current_user_session, :current_user
  filter_parameter_logging :password, :password_confirmation

  def new
    @channel = Channel.find(params[:channel_id])
    @user = current_user
    @channel.subscribers << @user
    @channel.save
    flash[:notice] = "You have subscribed to: " +@channel.name
    redirect_to @channel
  end

end

end

User Model

class User < ActiveRecord::Base

  acts_as_authentic

  ROLES = %w[admin  moderator subscriber]

  #Each user can subscribe to many channels
  has_many :channels_users
  has_many :subscriptions, :class_name => "Channel", :through => :channels_users

  #Each user who is a moderator can moderate many channels
  has_many :channel_mods
  has_many :channels, :through => :channel_mods

  #Each user can receive many messages
  has_ma开发者_如何学运维ny :messages_users , :dependent => :destroy
  has_many :reciepts , :class_name => "User", :through => :messages_users

  #Filter users by role(s)
  named_scope :with_role, lambda { |role| {:conditions => "roles_mask & #{2**ROLES.index(role.to_s)} > 0 "} }

  def roles  
    ROLES.reject { |r| ((roles_mask || 0) & 2**ROLES.index(r)).zero? }  
  end

  def roles=(roles)  
    self.roles_mask = (roles & ROLES).map { |r| 2**ROLES.index(r) }.sum  
  end

  def role_symbols
    role.map do |role|
      role.name.underscore.to_sym
    end
  end

end

Channel Model

class Channel < ActiveRecord::Base
  #Each channel owns many or no messages
  has_many :messages
  #Each channel is own by one moderator
  has_many :channel_mods
  has_many :moderators, :class_name =>'User', :through =>:channel_mod
  #Each channel can have and belong to many or no users
  has_many :channels_users
  has_many :subscribers, :class_name => 'Users' , :through => :channels_users

end

ChannelsUsers model

class ChannelsUsers < ActiveRecord::Base
  belongs_to :user
  belongs_to :channel
end

This would read much nicer if you change the model to ChannelUser. Here are the corresponding relationships:

class Channel < ActiveRecord::Base
  has_many :channel_users
  has_many :users, :through => :channel_users
end

class User < ActiveRecord::Base
  has_many :channel_users
  has_many :channels, :through => :channel_users
end

class ChannelUser < ActiveRecord::Base
  belongs_to :channel
  belongs_to :user
end

Your join table would then be called channel_users. I think you named it channels_users initially because that's the setup for a has_and_belongs_to_many join table. But since you're using has_many :through, you're free to name the table as you like.

I wrote a blog article earlier this year that walks through all the options in detail:

Basic Many-to-Many Associations in Rails

I hope this helps!

Your channel user class name is a plural. It is supposed to be singular.

So either you can change to this:

class ChannelsUser < ActiveRecord::Base
  belongs_to :user
  belongs_to :channel
end

or change this line in User and Channel model:

has_many :channels_users

to

has_many :channels_users, :class_name => 'ChannelsUsers'

Rails will use the methods like String#classify and String#underscore to detect classes and relationships.

If you want to play around with the names, in the console try out various combinations:

>> "channels_users".classify
=> "ChannelsUser"
>> "ChannelsUser".underscore
=> "channels_user"