Simple Mount Classes With CarrierWave

image.rb

class Image
  extend CarrierWave::Mount
  mount_uploader :image , ImageUploader
end

image_uploader.rb

class ImageUploader < CarrierWave::Uploader::Base
  include CarrierWave::MiniMagick
  storage :fog

  # Limit possible extensions
  def extension_white_list
    %w(jpg jpeg gif png)
  end

  # Set the storage directory
  def store_dir
    "images"
  end

  # Versions
  version :thumb do
    process :resize_to_fill => [200,132]
  end

end

sinatra_app.rb

class App < Sinatra::Base

  post "/upload/image" do

    # Example Image Handling Code
    img = Image.new
    img.image = params["file"]
    img.image.store! # => will save to S3!

    # do some other stuff....

  end

end