message system in ruby on rails

1- Create message model:- 

rails g model message sender_id:integer recepient_id:integer body:text

2- Define Assosciation and scopes:- 

class Message < ActiveRecord::Base
    belongs_to :sender,
     :class_name => 'User',
     :foreign_key => 'sender_id'
    belongs_to :recepient,
     :class_name => 'User',
     :foreign_key => 'recepient_id'

    scope :conversations, lambda{|sender_id,recepient_id| where('sender_id = ? AND recepient_id = ? ',sender_id, recepient_id ).order("created_at DESC")}

    scope :friends_conversations, lambda{|recepient_id,sender_id| where('sender_id = ? AND recepient_id = ? ',sender_id, recepient_id ).order("created_at DESC")}
end

3- User model:-

class User < ActiveRecord::Base
 has_many :received_messages,
 :class_name => 'Message',
 :foreign_key => 'recepient_id'
 has_many :sent_messages,
 :class_name => 'Message',
 :foreign_key => 'sender_id'
end

4- Return Conversations:- 

conversations = Message.conversations(current_user.id,params[:friend_id])
        friends_conversations = Message.friends_conversations(current_user.id,params[:friend_id])
        render :json =>  { status: 200,:conversations => (conversations + friends_conversations).sort_by(&:created_at) }

5- Return messages:-
messages = user.received_messages
sent_messages = user.sent_messages