Show the effects of method cache damage from runtime extend, as it relates to extend vs. delegate for DCI.

bm_dci_pounding.rb

require 'benchmark'

number_of_rails_methods = 300

@rails = Class.new do
  number_of_rails_methods.times do |i|
    class_eval <<-RUBY
      def call#{"%02d" % i}    # def call01
      end                   # end
    RUBY
  end
end.new

many_calls = Array.new(number_of_rails_methods) do |i|
  "@rails.call#{'%02d' % i}"
end.join("\n")

eval <<-RUBY
def rails_does_other_stuff
#{many_calls}
end
RUBY

Person = Struct.new(:first_name, :last_name)

class DelegateDecorator
  def initialize(target)
    @target = target
  end

  def method_missing(n, *a, &b)
    @target.__send__(n, *a, &b)
  end

  def full_name
    "#{first_name} #{last_name}"
  end
end

module DCIDecorator
  def self.new(object)
    object.extend(self)
    object
  end

  def full_name
    "#{first_name} #{last_name}"
  end
end

many = 100000

puts "# #{many} iterations"
puts "# #{number_of_rails_methods} non-decorated calls"

Benchmark.bmbm(20) do |r|

  r.report("plain dispatch") do
    many.times do
      person = Person.new("joe", "smith")
      rails_does_other_stuff
    end
  end

  r.report("some delegator") do
    many.times do
      person = Person.new("joe", "smith")
      decorated = DelegateDecorator.new(person)
      decorated.first_name
      decorated.full_name
      rails_does_other_stuff
    end
  end

  r.report("some dci decorator") do
    many.times do
      person = Person.new("joe", "smith")
      decorated = DCIDecorator.new(person)
      decorated.first_name
      decorated.full_name
      rails_does_other_stuff
    end
  end
end

results.txt

~ % ruby bm_dci_pounding.rb
# 100000 iterations
# 100 non-decorated calls
Rehearsal --------------------------------------------------------
plain dispatch         0.690000   0.000000   0.690000 (  0.688859)
some delegator         0.840000   0.010000   0.850000 (  0.848078)
some dci decorator     1.380000   0.000000   1.380000 (  1.379049)
----------------------------------------------- total: 2.920000sec

                           user     system      total        real
plain dispatch         0.700000   0.000000   0.700000 (  0.692977)
some delegator         0.850000   0.000000   0.850000 (  0.853181)
some dci decorator     1.420000   0.000000   1.420000 (  1.414180)
~ % ruby bm_dci_pounding.rb
# 100000 iterations
# 200 non-decorated calls
Rehearsal --------------------------------------------------------
plain dispatch         1.310000   0.010000   1.320000 (  1.315360)
some delegator         1.480000   0.000000   1.480000 (  1.485176)
some dci decorator     2.490000   0.010000   2.500000 (  2.493052)
----------------------------------------------- total: 5.300000sec

                           user     system      total        real
plain dispatch         1.320000   0.000000   1.320000 (  1.324366)
some delegator         1.490000   0.000000   1.490000 (  1.491190)
some dci decorator     2.510000   0.000000   2.510000 (  2.509399)
~ % ruby bm_dci_pounding.rb
# 100000 iterations
# 300 non-decorated calls
Rehearsal --------------------------------------------------------
plain dispatch         2.090000   0.010000   2.100000 (  2.099575)
some delegator         2.280000   0.010000   2.290000 (  2.283076)
some dci decorator     3.920000   0.010000   3.930000 (  3.925663)
----------------------------------------------- total: 8.320000sec

                           user     system      total        real
plain dispatch         2.080000   0.000000   2.080000 (  2.085480)
some delegator         2.300000   0.000000   2.300000 (  2.299252)
some dci decorator     3.950000   0.000000   3.950000 (  3.944498)
~ % ruby bm_dci_pounding.rb
# 100000 iterations
# 1000 non-decorated calls
Rehearsal --------------------------------------------------------
plain dispatch         7.190000   0.020000   7.210000 (  7.212247)
some delegator         7.320000   0.010000   7.330000 (  7.325742)
some dci decorator    12.940000   0.000000  12.940000 ( 12.940868)
---------------------------------------------- total: 27.480000sec

                           user     system      total        real
plain dispatch         7.250000   0.000000   7.250000 (  7.264858)
some delegator         7.450000   0.010000   7.460000 (  7.445777)
some dci decorator    13.060000   0.010000  13.070000 ( 13.070932)

What version of ruby did you run against?