Rake tasks from a Rubygem

While recently working on IronHide, specifically the CouchDB Adapter, I needed a way to have the gem expose custom Rake tasks to an end user’s application.

For example, to make working with the IronHide CouchDB Adapter easier, I wanted to allow users to upload existing rules from disk to a remote CouchDB database.

The task could be something as simple as:

$ bundle exec rake iron_hide:load_rules\['/absolute/path/file.json','http://127.0.0.1:5984/rules'\]

where the two arguments are the path to the JSON file and the remote CouchDB database.

Bundler #

After thinking for a moment, I knew that I’ve come across at least one gem that when included, exposes Rake tasks that I can use in my project, Bundler. So, I started looking through the source and found this: https://github.com/bundler/bundler/blob/master/lib/bundler/gem_helper.rb

Essentially, you’d like an application owner to be able to “install” a few Rake tasks at their convenience. Borrowing from the Bundler project:

# iron_hide/couchdb_tasks.rb
module IronHide
  class CouchDbTasks
    include Rake::DSL if defined? Rake::DSL

    def install_tasks
      namespace :iron_hide do
        desc 'Load rules from local JSON file to remote CouchDB server'
        task :load_rules, :file, :db_server do |t, args|
           ...
        end
      end
    end
  end
end

IronHide::CouchDbTasks.new.install_tasks

Now, in my application’s Rakefile I just need to add this line:

# Rakefile
require 'iron_hide/couchdb_tasks'

Et voila!

$ bundle exec rake -T

#=> rake iron_hide:load_rules[file,db_server]  # Load rules from local JSON