Rake Tasks from classes

rake.rb

# Use instance methods of classes as Rake tasks:
#
# In a folder tasks, create your classes.
#
# class FooTask
#   extend RakeDecorator
#
#   task :numbers, desc: 'A funny task that prints out the first 10 numbers'
#   def print_numbers_task
#     puts (1..10).to_a.join(',')
#   end
# end
#
require 'rake' unless defined?(Rake)
module RakeTasks

  @@tasks = {}

  module_function

  def add_task(task)
    task_class = task[:class].name
    if tasks.key?(task_class)
      tasks[task_class][:tasks] << task
    else
      tasks[task_class] = {
        tasks: [task]
      }
    end
  end

  def tasks
    @@tasks
  end
end

module RakeDecorator

  def task(name, *args)
    @_task = name
    @_desc = args.pop if args.last.is_a?(Hash)
    @_args = args
  end

  def desc(description)
    @_desc = {}; @_desc[:description] = description
  end

  def method_added(meth_name)
    RakeTasks.add_task(build_task_config(meth_name))
    %i(_task _args _desc).each { |ivar| instance_variable_set("@#{ivar}", nil) }
  end

  private def build_task_config(meth_name)
    task = {
      class: self,
      caller: self.instance_method(meth_name),
      task_name: @_task,
      arguments: @_args
      }
    task[:description] = @_desc[:desc] || @desc if @_desc
    task
  end
end

def LoadTasks(dir_path)
  Dir[dir_path].each do |file|
    require file unless File.directory?(file)
  end

  RakeTasks.tasks.each_pair do |task_class,value|
    tasks, instance = value[:tasks], Module.const_get(task_class).new
    tasks.each do |task|
      Rake.application.last_description = task[:description] if task[:description]
      caller = task[:caller]
      Rake::Task.define_task(task[:task_name], task[:arguments]) do |arg|
        caller.bind(instance).call
      end
    end
  end
end

dir_path = File.join(File.dirname(__FILE__), 'tasks', '**')
LoadTasks(dir_path)