DCI and Simple Facades

dci_stuff.rb

#
#  Comparison of a dumb facade implementation to #extend.
#  The principle advantage is that with caching it might be quicker that #extend,  
#  and it isolates the data_object so no behaviour 
#  changes persist after a context is finished.
#

require 'benchmark'
require 'singleton'

module Runner
  def run
    Math.tan(Math::PI / 4)
  end
end

class IncludeUser
  include Runner
end

class User
  def initiailize
    @one = :one
    @two = :two
    @three = :three
  end
end

class DCIClassCache
  include Singleton
  attr_reader :cache

  def initialize
    @cache = {}
  end

  def get_rolified_class(object, role)  
    klass = object.class
    role_name = role.name
    if @cache[klass] && @cache[klass][role_name]
      rolified_class = @cache[klass][role_name]
    else
      rolified_class = Class.new(object.class).send :include, role
      @cache[klass] ||= {}
      @cache[klass][role_name] = rolified_class
    end
  end
  
end

Benchmark.bm do |bench|
  3.times do
    bench.report('#include') do
      1000000.times do
        user = IncludeUser.new
        user.run
      end
    end
  end
end

Benchmark.bm do |bench|
  3.times do
    bench.report('#extend') do
      1000000.times do
        user = User.new
        user.extend Runner
        user.run
      end
    end
  end
end


Benchmark.bm do |bench|
  3.times do
    bench.report('dumb_facade_with_cache') do
      1000000.times do
        user = User.new

        # Get a 'template' class from a cache if it has been used before
        klass = DCIClassCache.instance.get_rolified_class( user , Runner)

        # instanciate facade object
        basic_facade = klass.new

        # copy the object's instance variables to the facade
        user.instance_variables.each do |ivar_name|
          ivar = user.instance_variable_get(ivar_name)
          basic_facade.instance_variable_set(ivar_name, ivar)
        end


        basic_facade.run

        # copy the facade's instance variables to the data object
        basic_facade.instance_variables.each do |ivar_name|
          ivar = basic_facade.instance_variable_get(ivar_name)
          user.instance_variable_set(ivar_name, ivar)
        end
      end
    end
  end
end


Benchmark.bm do |bench|
  3.times do
    bench.report('dumb_facade_without_cache') do
      1000000.times do
        user = User.new

        # Get a 'template' class from a cache if it has been used before
        # klass = DCIClassCache.instance.get_rolified_class( user , Runner)

        # instanciate facade object
        basic_facade = Class.new(user.class).send(:include, Runner).new

        # copy the object's instance variables to the facade
        user.instance_variables.each do |ivar_name|
          ivar = user.instance_variable_get(ivar_name)
          basic_facade.instance_variable_set(ivar_name, ivar)
        end


        basic_facade.run

        # copy the facade's instance variables back to the object
        basic_facade.instance_variables.each do |ivar_name|
          ivar = basic_facade.instance_variable_get(ivar_name)
          user.instance_variable_set(ivar_name, ivar)
        end
      end
    end
  end
end

#     Benchmarks ruby 1.9.3p125 (2012-02-16 revision 34643) [x86_64-darwin11.3.0]
#
#             user     system      total        real
#      #include  0.700000   0.000000   0.700000 (  0.719030)
#      #include  0.640000   0.000000   0.640000 (  0.640602)
#      #include  0.640000   0.000000   0.640000 (  0.638456)
#             user     system      total        real
#      #extend  3.830000   0.010000   3.840000 (  3.875515)
#      #extend  3.900000   0.000000   3.900000 (  3.958716)
#      #extend  3.810000   0.010000   3.820000 (  3.835442)
#             user     system      total        real
#      dumb_facade_with_cache  2.500000   0.000000   2.500000 (  2.658489)
#      dumb_facade_with_cache  2.330000   0.010000   2.340000 (  2.335742)
#      dumb_facade_with_cache  2.340000   0.000000   2.340000 (  2.352163)
#             user     system      total        real
#      dumb_facade_without_cache  7.450000   0.010000   7.460000 (  7.683932)
#      dumb_facade_without_cache  7.370000   0.010000   7.380000 (  7.519060)
#      dumb_facade_without_cache  7.360000   0.010000   7.370000 (  7.559644)