is_fast_enough.rb

# Check the impact of Nokogiri builder / HAML engine caching
require 'benchmark'
require 'sinatra-nokogiri-menu.rb'
require 'haml'

def render_with_haml(current = nil)
  @engine ||= Haml::Engine.new <<here
%ul
  - MENU_ITEMS.each do |item|
    - opts = {}
    - item, check_proc = *item if item.is_a?(Array)
    - if check_proc.nil? or check_proc.call
      - if current.to_s == item.to_s
        %li{:class => 'current_item'}
          = item.to_s
      - else
        %li= item.to_s
  %li world
here
  @engine.render(Object.new, :current => current)
end

#        doc.li item.to_s, opts
puts render_with_haml(:contact)


puts
puts "Compare different approaches running 1000 times:\n"

Benchmark.bm(30) do |b|
  b.report('Nokogiri, singleton builder') do
    1000.times{ main_menu(:contact) }
  end

  b.report('Nokogiri, recreate builder') do
    1000.times{ main_menu(:contact); @main_menu_builder = nil }
  end

  b.report('HAML, singleton engine') do
    1000.times{ render_with_haml(:contact) }
  end

  b.report('HAML, recreate engine') do
    1000.times{ render_with_haml(:contact); @engine = nil }
  end
end

sinatra-nokogiri-menu.rb

# Generates a menu for your web site.
# Features:
# * current menu item highlighting
# * dynamic list of menu items, based on your application logic,
#   controlled by user provided procs
require 'rubygems'
require 'nokogiri'

# current_user is mocked here, use you real implementation instead
current_user = Object.new
def current_user.has_role?(role); false; end
def current_user.is_admin?; true; end

MENU_ITEMS = [
  :orders,
  [:customers, Proc.new {current_user.has_role?(:supervisor)}],
  [:admin, Proc.new {current_user.is_admin?}],
  :contact
]

def main_menu(current=nil)
  @main_menu_builder ||= Nokogiri::HTML::Builder.new do |doc|
    doc.ul {
      MENU_ITEMS.each do |item|
        opts = {}
        item, check_proc = *item if item.is_a?(Array)
        opts[:class] = 'current_item' if current.to_s == item.to_s
        doc.li item.to_s, opts if check_proc.nil? or check_proc.call
      end
    }
  end
  @main_menu_builder.doc.inner_html
end

puts main_menu(:contact)

# generates:

# <ul>
# <li>orders</li>
# <li>admin</li>
# <li class="current_item">contact</li>
# </ul>