Please HELP me! I'm stuck on the Mutual Friendships video.

class UserFriendship < ActiveRecord::Base
  belongs_to :user
  belongs_to :friend, class_name: 'User', foreign_key: 'friend_id'

   state_machine :state, initial: :pending do

    after_transition on: :accept, do: [:send_acceptance_email, :accept_mutual_friendship!]

    state :requested

    event :accept do
        transition any => :accepted
    end
  end

  def self.request(user1, user2)
    transaction do
        friendship1 = create!(user: user1, friend: user2, state: 'pending')
        friendship2 = create!(user: user2, friend: user1, state: 'requested')

        friendship1.send_request_email
        friendship1
    end    
  end


 def send_request_email
    UserNotifier.friend_requested(id).deliver
 end

 def send_acceptance_email
    UserNotifier.friend_request_accepted(id).deliver
 end

 def mutual_friendship
 self.class.where({user_id: friend_id, friend_id: user_id}).first
 end

  def accept_mutual_friendship!
  # Grab the mutual friendship and update the state without using the state machine, so as
  # not to invoke callbacks.
  mutual_friendship.update_attribute(:state, 'accepted')
  end 
end

 class UserFriendshipsController < ApplicationController
 before_filter :authenticate_user!

  def index
  @user_Friendships = current_user.user_friendships.all
  end   

 def accept
  @user_friendship = current_user.user_friendships.find(params[:id])
  if @user_friendship.accept_mutual_friendship!
  flash[:success] = "You are now friends with #{@user_friendship.friend.name}"
  redirect_to user_friendships_path
 else
  flash[:error] = "That friendship could not be accepted"
  redirect_to user_friendships_path
  end
end

 def new
 if params[:friend_id]
   @friend = User.find(params[:friend_id])
   raise ActiveRecord::RecordNotFound if @friend.nil?
    @user_friendship = current_user.user_friendships.new(friend: @friend)
 else
  flash[:error] = "Friend required"
  end
  rescue ActiveRecord::RecordNotFound
  render file: 'public/404', status: :not_found
 end

  def create
  if params[:user_friendship] && params[:user_friendship].has_key?(:friend_id)
  @friend = User.find(params[:user_friendship][:friend_id])
  @user_friendship = UserFriendship.request(current_user, @friend)
  if @user_friendship.new_record?
    flash[:error] = "There was a problem creating this friend request."
  else
    flash[:success] = "Friend request sent."
  end
  redirect_to user_path(@friend)
 else
  flash[:error] = "Friend required"
  redirect_to root_path
   end
 end

def edit
@user_friendship = current_user.user_friendships.find(params[:id])
@friend = @user_friendship.friend
end

 def user_friendship
  params.require(:user_friendship).permit(:user_id, :friend_id, :user, :friend, :state, :user_friendship)
  end    
 end