Rails Image Upload

model.rb

module Tokenable
  extend ActiveSupport::Concern

  included do
    before_validation :generate_token
    validates :token, presence: true, uniqueness: true
  end

protected

  def generate_noise
    SecureRandom.urlsafe_base64(nil, false).gsub(/[-_]+/,'').downcase
  end

  def generate_token
    return if self.token.present?
    random_token = self.generate_noise[0,4]

    self.token = loop do
      break random_token unless self.class.exists?(token: random_token)
      random_token += self.generate_noise[0,2]
    end
  end
end

class GalleryImage < ActiveRecord::Base

  include Tokenable

  mount_uploader :image, DigestUploader

end

uploader.rb

class DigestUploader < CarrierWave::Uploader::Base

  include CarrierWave::MiniMagick
  process :store_details

  storage :fog

  def store_dir
    "gallery/#{model.token}"
  end

  def filename
    "o.#{model.image.file.extension}"
  end

  def extension_white_list
    %w(jpg jpeg gif png)
  end

  version :phone, :if => :resizable? do
    process :resize_to_limit => [750, nil]

    def full_filename(for_file = model.logo.file)
      "p.#{model.image.file.extension}"
    end
  end

  version :favorite, :if => :resizable? do
    process :resize_to_fill => [300,300]

    def full_filename(for_file = model.logo.file)
      "f.#{model.image.file.extension}"
    end
  end

  def resizable? picture
    picture.content_type.index("gif").nil?
  end

private

  def store_details
    if file && model
      model.content_type = file.content_type if file.content_type
      model.file_size = file.size
      model.width, model.height = ::MiniMagick::Image.open(file.file)[:dimensions]
    end
  end

end