Rails 3: Couldn't find User without an ID - ruby-on-rails

Question

Hi I'm currently working on my first rails project (a photo uploading site), and am getting an error on a form that creates a new photo album that belongs to a user. I'm trying to use the Paperclip gem. It's giving me the error:
ActiveRecord::RecordNotFound in AlbumsController#create
Couldn't find User without an ID
I'm guessing it has something to do with the instance variables in my create action, but I don't see what's wrong. Any guidance would be helpful. Here are my files:
_form.html.erb
<%= form_for (#album), :remote => true, :html => { :id => "uploadform", :multipart => true } do |f| %>
<div>
<%= f.label :name %>
<%= f.text_field :name %>
<%= f.label :description %>
<%= f.text_area :description %>
<%= f.fields_for :avatar do |avatar_form| %>
<%= avatar_form.label :avatar, "Upload" %>
<%= avatar_form.file_field :avatar, :multiple => true %>
<% end %>
<%=f.submit %>
</div>
<% end %>
albums_controller create action:
def create
#users = User.all
#user = User.find(params[:user_id])
#album = #user.albums.build(params[:album])
if #album.save
flash[:success] = "Album created!"
end
end
config/routes
Pholder::Application.routes.draw do
resources :users do
resources :albums
end
resources :albums do
resources :pictures
end
Album model
class Album < ActiveRecord::Base
attr_accessible :avatar, :name, :description
has_and_belongs_to_many :users
has_attached_file :avatar
end
Let me know if you need to see any other files.

Answer 1

Since this is a new album, there is no user_id in the albums hash as I first thought. I added a new method that merges in the user id to the hash.
def create
#users = User.all
#album = Album.new(params[:album].merge!(:user_id => current_user))
if #album.save
flash[:success] = "Album created!"
end
end
If you would rather not have user_id in attr_accessible in your Album model, you can assign it separately.
def create
#users = User.all
#album = Album.new(params[:album])
#album.user_id = current_user.id
if #album.save
flash[:success] = "Album created!"
end
end