title: Carrierwave cannot remove image
body: <p>I'm using Carrierwave for uploading image now. All nice, except one, - when I add checkbox for removing uploaded image I get error: "Can't mass-assign protected attributes: remove_image".</p>
  
  <p>Form:</p>
  
  <pre><code>...
  &lt;%= f.check_box :remove_image %&gt;
  &lt;%= f.label :remove_image, "remove image" %&gt;
  ...
  </code></pre>
  
  <p>Model:</p>
  
  <pre><code>class Manufacturer &lt; ActiveRecord::Base
  
    attr_accessible :name, :alias, :short_description, :long_description, :image, :publish,
    :position, :meta_keywords, :meta_description, :meta_title
  
    mount_uploader :image, ManufacturerUploader
  
    validates_presence_of :name, :alias
    validates_uniqueness_of :name, :alias
    validates_format_of :alias, :with =&gt; /^[a-z\d\-]*$/, :message =&gt; "a-z, 0-9 \' - \' ONLY"
  
    default_scope order('position ASC')
  
    before_destroy :remember_image
    after_destroy :remove_img
  
    protected
    def remember_image
      @image_name = self[:image]
    end
  
    def remove_img
      File.delete("#{Rails.root}/public/images/manufacturer/#{@image_name}")
      File.delete("#{Rails.root}/public/images/manufacturer/thumb_#{@image_name}")
    end
  
  end
  </code></pre>
  
  <p>Uploader:</p>
  
  <pre><code>class ManufacturerUploader &lt; CarrierWave::Uploader::Base
  
   include CarrierWave::MiniMagick
   include Sprockets::Helpers::RailsHelper
   include Sprockets::Helpers::IsolatedHelper
  
   storage :file
  
   before :store, :remember_cache_id
   after :store, :delete_tmp_dir
  
   def remember_cache_id(new_file)
     @cache_id_was = cache_id
   end
  
   def delete_tmp_dir(new_file)
     if @cache_id_was.present? &amp;&amp; @cache_id_was =~ /\A[\d]{8}\-[\d]{4}\-[\d]+\-[\d]{4}\z/
        FileUtils.rm_rf(File.join(root, cache_dir, @cache_id_was))
     end
   end
  
  def store_dir
    "images/#{model.class.to_s.underscore}"
  end
  
  def default_url
    "" + [version_name, "default.jpg"].compact.join('_')
  end
  
  process :resize_to_fit =&gt; [300, 300]
  
  version :thumb do
     process :resize_to_fit =&gt; [150, 150]
  end
  
  def extension_white_list
     %w(jpg jpeg gif png)
  end
  
  def filename
    "#{secure_token(10)}.#{file.extension}" if original_filename.present?
  end
  
  protected
  def secure_token(length=16)
    var = :"@#{mounted_as}_secure_token"
    model.instance_variable_get(var) or model.instance_variable_set(var, SecureRandom.hex(length/2))
  end
  
  end
  </code></pre>
  
  <p>I think Carrierwave must to leverage :remove_image, but don't do it. What's wrong in this code?</p>