delegate-bench.rb

begin
  require 'bundler/inline'
rescue LoadError => e
  $stderr.puts 'Bundler version 1.10 or later is required. Please update your Bundler'
  raise e
end

gemfile(true) do
  source 'https://rubygems.org'
  gem 'activesupport', '5.0.0rc1'
  gem 'benchmark-ips'
end

require 'benchmark/ips'
require 'active_support/all'

class Module
  def optimized_delegate(*methods, to: nil, prefix: nil, allow_nil: nil)
    unless to
      raise ArgumentError, 'Delegation needs a target. Supply an options hash with a :to key as the last argument (e.g. delegate :hello, to: :greeter).'
    end

    if prefix == true && to =~ /^[^a-z_]/
      raise ArgumentError, 'Can only automatically set the delegation prefix when delegating to a method.'
    end

    method_prefix = \
      if prefix
        "#{prefix == true ? to : prefix}_"
      else
        ''
      end

    location = caller_locations(1, 1).first
    file, line = location.path, location.lineno

    to = to.to_s
    to = "self.#{to}" if DELEGATION_RESERVED_METHOD_NAMES.include?(to)

    methods.each do |method|
      # Attribute writer methods only accept one argument. Makes sure []=
      # methods still accept two arguments.
      definition = (method =~ /[^\]]=$/) ? 'arg' : '*args, &block'

      # The following generated method calls the target exactly once, storing
      # the returned value in a dummy variable.
      #
      # Reason is twofold: On one hand doing less calls is in general better.
      # On the other hand it could be that the target has side-effects,
      # whereas conceptually, from the user point of view, the delegator should
      # be doing one call.
      if allow_nil
        method_def = [
          "def #{method_prefix}#{method}(#{definition})",
          "_ = #{to}",
          "if !_.nil? || nil.respond_to?(:#{method})",
          "  _.#{method}(#{definition})",
          "end",
        "end"
        ].join ';'
      else
        exception = %(raise DelegationError, "#{self}##{method_prefix}#{method} delegated to #{to}.#{method}, but #{to} is nil: \#{self.inspect}")

        method_def = [
          "def #{method_prefix}#{method}(#{definition})",
          " _ = #{to}",
          "  _.#{method}(#{definition})",
          "rescue NoMethodError => e",
          "  if _.nil? && e.name == :#{method}",
          "    #{exception}",
          "  else",
          "    raise",
          "  end",
          "end"
        ].join ';'
      end

      module_eval(method_def, file, line)
    end
  end
end


def bench_delegate
  Class.new do
    delegate :foo, to: :@bar
  end
end

def bench_optimized_delegate
  Class.new do
    optimized_delegate :foo, to: :@bar
  end
end

Benchmark.ips do |x|
  x.report('as::delegate') do
    bench_delegate
  end

  x.report('op::delegate') do
    bench_optimized_delegate
  end
end

result.md

Fetching gem metadata from https://rubygems.org/ Fetching version metadata from https://rubygems.org/ Resolving dependencies... Using concurrent-ruby 1.0.2 Using i18n 0.7.0 Using minitest 5.9.0 Using thread_safe 0.3.5 Using benchmark-ips 2.6.1 Using bundler 1.12.3 Using tzinfo 1.2.2 Using activesupport 5.0.0.rc1 Warming up -------------------------------------- as::delegate 1.855k i/100ms op::delegate 2.080k i/100ms Calculating ------------------------------------- as::delegate 20.128k (± 5.6%) i/s - 102.025k in 5.082693s op::delegate 20.725k (± 9.6%) i/s - 104.000k in 5.073423s