title: Asset model missing required attr_accessor with Paperclip
body: <p>I am trying to upload more than 1 file asset to a movie. I keep receiving an error <code>Asset model missing required attr_accessor for 'asset_file_name'</code> and I am not sure why, here is my code:</p>
  
  <p>asset.rb model</p>
  
  <pre><code>class Asset &lt; ActiveRecord::Base
    belongs_to :movie
  
    has_attached_file :asset
  end
  </code></pre>
  
  <p>movie.rb model</p>
  
  <pre><code>class Movie &lt; ActiveRecord::Base
    belongs_to :user
  
    has_many :assets
    accepts_nested_attributes_for :assets
  
    validates :title, presence: true
  
    default_scope order: 'movies.created_at DESC'
  end
  </code></pre>
  
  <p>I have also ran <code>rails g paperclip movie asset</code> which generated the following migration file</p>
  
  <pre><code>class AddAttachmentAssetToMovie &lt; ActiveRecord::Migration
    def self.up
      add_column :movies, :asset_file_name, :string
      add_column :movies, :asset_content_type, :string
      add_column :movies, :asset_file_size, :integer
      add_column :movies, :asset_updated_at, :datetime
    end
  
    def self.down
      remove_column :movies, :asset_file_name
      remove_column :movies, :asset_content_type
      remove_column :movies, :asset_file_size
      remove_column :movies, :asset_updated_at
    end
  end
  </code></pre>
  
  <p>And here is my "create assets" migration that came from when I generated the asset model:</p>
  
  <pre><code>class CreateAssets &lt; ActiveRecord::Migration
    def change
      create_table :assets do |t|
      t.string :asset_file_name
      t.integer :asset_file_size
      t.string :asset_content_type
      t.datetime :asset_updated_at
      t.text :asset_description
      t.integer :movie_id
  
      t.timestamps
    end
  end
  </code></pre>
  
  <p>Can any suggest why i would be receiving the error <code>Asset model missing required attr_accessor for 'asset_file_name'</code>?</p>