File downloads

class DownloadsController < ApplicationController
  include Hydra::Controller::DownloadBehavior
end

then in config/routes.rb add resources :downloads

then you can do a GET /downloads/{pid}?datastream_id=thumbnail to get the thumbnail datastream

By default this allows any user with read access to the object identified by pid to download any of the datastreams. If you want to control which datastreams a user has access to:

In hydra-head versions >= 7.0, override the download_permissions method of Hydra::Ability

# This example allows anyone to download a 'thumbnail' datastream
# and requires read access to download other datastreams
def download_permissions
  can :download, ActiveFedora::Datastream do |ds|
    ds.dsid == 'thumbnail' || can?(:read, ds.pid)
  end
end

In hydra-head versions < 7.0, override the can_download? method of Hydra::Controller::DownloadBehavior.

# This example allows anyone to download a 'thumbnail' datastream
def can_download?
  datastream.dsid == 'thumbnail'
end