Rails, Nested Models, Arrays, Iterating through a "for" loop - ruby-on-rails

Question

I'm new to Ruby and following this novawave tutorial (a little older) on creating an internal messaging system.
http://www.novawave.net/public/rails_messaging_tutorial.html
I'm currently attempting to list the sent messages, but I am unable to properly link to the message "recipients." Here is the for loop:
<% for message in #messages %>
<tr>
<td><%= message.user.name %></td>
<td><%= message.subject %></td>
<td><%= message.recipients.map(&:user).to_sentence %></td>
I'm getting an "unitialized constant" error for "recipients" I have three models: User, Message_Copy, and Message.
Message Model
belongs_to User,
has_many :recipients, :through => :message_copies
Message_Copy model
belongs_to Message and recipient
User model
has_many of the other models.
I've noticed this same problem in other applications. When I iterate through the array, if the primary model "belongs to" another model, I can access that model. For example, I can access the User model because the Message model "belongs_to" the User model. Hence I can use message.user.name. But I cannot access the attributes of a model that "belongs_to" the primary model. So I cannot access the Message_Copy model attributes in this array. So message.recipient.id will return an error. This question may have already been answered, and I may just be making a series of easy mistakes. But I'm confused and was hoping someone could help and possibly explain what I'm missing. Please let me know if more informaiton is required. Thank you
Apologies, here is more code from the models:
User Model
class User < ActiveRecord::Base
attr_accessor :password
attr_accessible :name, :email, :password, :password_confirmation
has_many :sent_messages, :class_name => "Message"
has_many :received_messages, :class_name => "MessageCopy", :foreign_key =>"recipient_id"
has_many :folders
class MessageCopy < ActiveRecord::Base
belongs_to :message
belongs_to :recipient
belongs_to :folder
delegate :user, :created_at, :subject, :body, :recipients, :to => :message
end
class Message < ActiveRecord::Base
belongs_to :user
has_many :message_copies
has_many :recipients, :through => :message_copies
before_create :prepare_copies
attr_accessor :to # array of people to send to
attr_accessible :subject, :body, :to
def prepare_copies
return if to.blank?
to.each do |recipient|
recipient = User.find(recipient)
#recipient=recipient
message_copies.build(:recipient_id => recipient.id, :folder_id => recipient.inbox.id)
end
end
end
I noticed this worked:
<%= message.message_copies %>
Instead of the above code:
<td><%= message.recipients %></td>
I don't understand this because the tutorial can use "recipients" and also because I can reference the Message_Copy model through Recipients in other methods.
But
<%= message.message_copies %>
also just returns an array, and I'm unclear how I can reach the specific attributes in the message_copy model, since
<%= message.message_copies.content %>
does not work.
Thank you! I'll post more code if necessary