My ImageUploader.rb class

image_uploader.rb

# encoding: utf-8

class ImageUploader < CarrierWave::Uploader::Base

  include CarrierWave::RMagick

  # Choose what kind of storage to use for this uploader:
  #storage :file
  storage :fog

  # Override the directory where uploaded files will be stored.
  # This is a sensible default for uploaders that are meant to be mounted:
  def store_dir
    "#{model.class.to_s.underscore.pluralize}/#{model.id}/images"
  end

  # Provide a default URL as a default if there hasn't been a file uploaded:
  def default_url
    "/images/noimage.png"
  end

  # Process files as they are uploaded:
  # process :scale => [200, 300]
  #
  # def scale(width, height)
  #   # do something
  # end

  # Create different versions of your uploaded files:
  version :thumb do
    process :resize_to_limit => [300, 200]
  end

  # Add a white list of extensions which are allowed to be uploaded.
  # For images you might use something like this:
  def extension_white_list
    %w(jpg jpeg gif png)
  end

  # Override the filename of the uploaded files:
  # Avoid using model.id or version_name here, see uploader/store.rb for details.
  # def filename
  #   "something.jpg" if original_filename
  # end

end