From: Trans <transfire@...>
Date: 2006-04-26T10:14:52+09:00
Subject: Re: Rake task dependeny vs. method call

Just for fun I put together this simple demonstration.

# --- task.rb

require 'facet/module/memoize'

module Task

  # Store the dependencies.

  def task_dependencies
    @task_dependencies ||= {}
  end

  # Store the decriptions.

  def task_descriptions
    @task_descriptions ||= {}
  end

  # Set the description of the subsequent task.

  def desc( line )
    @last_description = line.gsub("\n",'')
  end

  # Define a task.

  def task( args, &action )

    if Hash === args
      raise ArgumentError, "#{args.size} for 1" if args.size != 1
      name, deps = *(args.to_a.flatten)
      name = name.to_sym
      deps = [deps].compact.collect{ |e| e.to_sym }
    else
      name, deps = args.to_sym, []
    end

    task_dependencies[ name ] = deps
    task_descriptions[ name ] = @last_description
    @last_description = nil

    (class << self; self; end).class_eval do

      define_method( name ) do
        deps.each{ |d| send(d) }
        action.call
      end

      memoize name

    end

  end

end

include Task

desc "Milk the cow!"
task :milk do
  puts "milk"
end

desc "Jump over the moon!"
task :jump => [ :milk, :milk ] do
  milk; milk
  puts "jump"
end

jump

puts task_descriptions[:milk]
puts task_descriptions[:jump]