DataMapper extensions to support the Rack-based file storing/processing library, Dragonfly.
Require dm-dragonfly and create a new Dragonfly app with the desired configuration options. Define a macro for the Dragonfly app using the added Dragonfly::App#define_dm_macro method. Define this on the base module that you're including in all models (likely a custom module you've written or DataMapper::Resource).
require 'dm-dragonfly'
app = Dragonfly[:attachments]
app.configure_with(:imagemagick)
app.configure_with(:rails)
app.define_dm_macro(BaseModel, :attachment_accessor)