Rails association cannot be blank - ruby-on-rails

Question

I'm building off the tutorial app in ruby on rails for a project, and I'm trying to create an association between two models.
In my database, there are users, events, and an attendance table that associates with the email from a user and a code from an event.
I've tried to research how to do this myself, but every time I try to validate the attendance email to a user, it states that the user cannot be blank as if I were trying to create a new one.
Still quite new to Ruby on Rails, so any advice would be appreciated! The models are below.
User Model:
class User < ActiveRecord::Base
attr_accessible :email, :name, :password, :password_confirmation
has_secure_password
has_many :attendances, inverse_of: :user
accepts_nested_attributes_for :attendances
before_save { |user| user.email = email.downcase }
before_save :create_remember_token
VALID_EMAIL_REGEX = /\A[\w+\-.]+#[a-z\d\-.]+\.[a-z]+\z/i
validates(:name, presence: true, length: { maximum: 50 })
validates(:email, presence: true, format: { with: VALID_EMAIL_REGEX }, uniqueness: {case_sensitive: false})
validates(:password, length: { minimum: 6 } )
validates(:password_confirmation, presence: true)
private
def create_remember_token
self.remember_token = SecureRandom.urlsafe_base64
end
end
Attendance Model:
class Attendance < ActiveRecord::Base
attr_accessible :code, :email
belongs_to :user
validates_presence_of :user
end
So far I'm only trying to enforce the association between User and Attendance, once I get that working I'll do the same to Events. Also, this is Rails 3.2.19 and Ruby 1.9.3.
EDIT: Here is the code I'm using for the form, I believe that it works because until I put the validation into the model it was creating rows into the Attendance table.
<% provide(:title, 'Test Event') %>
<h1>Attendance Registration</h1>
<div class="row">
<div class="span6 offset3">
<%= form_for(#attendance) do |f| %>
<%= render 'shared/attendance_error_messages' %>
<%= f.label :email %>
<%= f.text_field :email %>
<%= f.label :code %>
<%= f.text_field :code %>
<%= f.submit "Submit", class: "btn btn-large btn-primary" %>
<% end %>
</div>
</div>
Also, here's the attendance controller, if that helps.
class AttendancesController < ApplicationController
def new
#attendance = Attendance.new
end
def create
#attendance = Attendance.new(params[:attendance])
if #attendance.save
flash[:success] = "Attendance logged."
redirect_to root_path
else
render 'new'
end
end
end

Answer 1

Add this line to your form to avoid the user presence error
<%= f.hidden_field :user_id, current_user.id %>