OnRails.org

Here we go again RailsConf 2010 has started. The keynotes will be streamed online at http://railsconf.com and the slides of the presentation will also be posted there. I’ll provide more links once they become available.

This is the view from my hotel which is 5 minutes from the convention center where RailsConf is going on.

Acceptance Testing with Cucumber

I’m now following the Acceptance Testing with Cucumber tutorial. You can find the app we built, a kanban manager, on github.

Cucumber is executable documentation. Gurken is the DSL used to write your documentation in the form of

Scenario:
  Given
  When
  Then

The app has different git branches for each stage of the application. Checkout the move-card-passing branch for the most complete functionality. It contains great examples of feature test.

   master                               f294f72 patch number

   remotes/origin/HEAD                  → origin/master

   remotes/origin/first-feature-failing 475eb7e words

   remotes/origin/first-feature-passing e4ea67a gemfile

   remotes/origin/latest                eacd855 Merge

   remotes/origin/master                f294f72 patch number

   remotes/origin/more-features-failing aa2d97b new failing features

   remotes/origin/more-features-passing 03b6b44 added lane ordering

   remotes/origin/move-card-failing     02fa766 add move_card feature


	
remotes/origin/move-card-passing     8c1d751 move cards from one lane to another

BUILDING AN API WITH RAILS

A great discussion on building APIs using Ruby and Rails:

• joshowens – Four Bean Soup
• joeferris – thoughtbot
• bitsweat – 37signals
• noradio – twitter
• technoweenie – GitHub
• derekwillis – The New York Times

Sneak peek of Usage Report for Amazon Web Services??????? from daniel wanja.

The conference is about to start in 30 minutes, the room starts to buzz. The confreaks guys have their camera and video recording equipment all setup. So you will be able to catch up the conference online soon. Somehow I really like single track conferences and the sessions seem really great and will be fast passed, 30 to 45 minutes. Check out the schedule. So I will sit back and enjoy the show.

Follow it live on Justin TV!!

Watch live video from Mountain West Ruby Conference on Justin.tv

Salt Lake City is definitively a beautiful city, surrounded by it’s mountains…

After the release of 10.5, I published an article about building RMagick from source on Leopard. I won’t rehash the why, you can read the original article for that. My clean install necessitated updating the RMagick script, so here’s what worked for me to install from source on Snow Leopard! For the impatient, here’s the download link: rmagick-build.sh

First, we start with installing wget, as it seems to be a bit more clever than curl about dealing with mirrors, etc. Then, we compile and install each prerequisite package. Finally, we install the gem.

All the links in the script worked for me, but, depending on your location, network, conditions, etc, your mileage may vary. Enjoy!

#!/bin/sh

# install wget, which is cleverer than curl
curl -O http://ftp.gnu.org/gnu/wget/wget-1.11.tar.gz
tar zxvf wget-1.11.tar.gz 
cd wget-1.11
./configure --prefix=/usr/local
make
sudo make install
cd /usr/local/src

# prerequisite packages
wget http://nongnu.askapache.com/freetype/freetype-2.3.9.tar.gz
tar zxvf freetype-2.3.9.tar.gz
cd freetype-2.3.9
./configure --prefix=/usr/local
make
sudo make install
cd /usr/local/src

wget http://superb-west.dl.sourceforge.net/sourceforge/libpng/libpng-1.2.39.tar.gz
tar zxvf libpng-1.2.39.tar.gz
cd libpng-1.2.39
./configure --prefix=/usr/local
make
sudo make install
cd /usr/local/src

wget ftp://ftp.uu.net/graphics/jpeg/jpegsrc.v6b.tar.gz
tar xzvf jpegsrc.v6b.tar.gz
cd jpeg-6b
ln -s `which glibtool` ./libtool
export MACOSX_DEPLOYMENT_TARGET=10.6
./configure --enable-shared --prefix=/usr/local
make
sudo make install
cd /usr/local/src

wget ftp://ftp.remotesensing.org/libtiff/tiff-3.9.1.tar.gz
tar xzvf tiff-3.9.1.tar.gz
cd tiff-3.9.1
./configure --prefix=/usr/local
make
sudo make install
cd /usr/local/src

wget http://superb-west.dl.sourceforge.net/sourceforge/wvware/libwmf-0.2.8.4.tar.gz
tar xzvf libwmf-0.2.8.4.tar.gz
cd libwmf-0.2.8.4
make clean
./configure
make
sudo make install
cd /usr/local/src

wget http://www.littlecms.com/lcms-1.17.tar.gz
tar xzvf lcms-1.17.tar.gz
cd lcms-1.17
make clean
./configure
make
sudo make install
cd /usr/local/src

wget ftp://mirror.cs.wisc.edu/pub/mirrors/ghost/GPL/gs870/ghostscript-8.70.tar.gz
tar zxvf ghostscript-8.70.tar.gz
cd ghostscript-8.70
./configure  --prefix=/usr/local
make
sudo make install
cd /usr/local/src

wget ftp://mirror.cs.wisc.edu/pub/mirrors/ghost/GPL/gs860/ghostscript-fonts-std-8.11.tar.gz
tar zxvf ghostscript-fonts-std-8.11.tar.gz
sudo mv fonts /usr/local/share/ghostscript

# Image Magick
wget ftp://ftp.fifi.org/pub/ImageMagick/ImageMagick.tar.gz
tar xzvf ImageMagick.tar.gz
cd `ls | grep ImageMagick-`
export CPPFLAGS=-I/usr/local/include
export LDFLAGS=-L/usr/local/lib
./configure --prefix=/usr/local --disable-static --with-modules --without-perl --without-magick-plus-plus --with-quantum-depth=8 --with-gs-font-dir=/usr/local/share/ghostscript/fonts --disable-openmp
make
sudo make install
cd /usr/local/src

# RMagick
sudo gem install rmagick

UPDATE There is a bug with libgomp that breaks the convert utility (See comments below). the --disable-openmp configure option has been added to the script to fix this.

UPDATE 2 A new patchlevel of ImageMagick has been released that supersedes the original one referenced in this script, and the original has been removed from the server. Thanks to Sebastian for this update that will grab the latest release.

The Confreaks guys did setup their cameras, sound and lights, so you will certainly be able to see all the talks in a few weeks.

The conference takes place in Salt Lake City, the scenery is impressive as the city is surrounded by high mountains…even for someone living in Denver. The picture above was taken just before the conference starts and shows the atrium we gonna spend the next two days in. The talks looks really cool and tonight the Engine Yard’s Hackfest 2.0 in suite next to mine at the Hilton Salt Lake City Center.

The first two days of the training were really excellent. Great pace, clear explanations and samples, very technical, Chad and Dave really rock at Ruby.

Making Domain-Specific Languages

We start with a discussion on DSL versus an API.

Meat-and-Potato DSLs

• Block based API.
• Directly manipulating domain model classes
• Defining classes and methods
• Manually typing repetitive, low-level code

Example is Rake. Rake is a dependency oriented programming language.

Eexample from Dhaka (a paraser generator)

for_pattern("\n") do
 create_token("newline")
end

method_missing Trick

require 'pp'

class CommandListener
  def initialize
    @commands = []
  end
    
  def method_missing(*args)
    @commands << args
    self
  end
end

listener = CommandListener.new

listener.instance_eval do
  this object accepts whatever you type and stores it
end
pp listener

outputs:

#<CommandListener:0x80264
 @commands=
  [[:you, CommandListener],
   [:whatever, #<CommandListener:0x80264 ...>],
   [:accepts, #<CommandListener:0x80264 ...>],
   [:object, #<CommandListener:0x80264 ...>],
   [:this, #<CommandListener:0x80264 ...>],
   [:it],
   [:stores, #<CommandListener:0x80264 ...>]]>

listener = CommandListener.new
listener.instance_eval do
  this.object.accepts.whatever.commands.and.stores.it
end  

pp listener

outputs:

#<CommandListener:0x712b4
 @commands=
  [[:this],
   [:object],
   [:accepts],
   [:whatever],
   [:commands],
   [:and],
   [:stores],
   [:it]]>

Note any keyword can be used with method_missing…E.g. freeze is not a missing method.

Now by using a BlankSlate object we can avoid this issue:

class BlankSlate
  instance_methods.each do |method|
    undef_method(method) unless method =~ /^__/ || method == 'instance_eval'
   end
end

We can now create a command listener that can use any commands:

require 'pp'

class CommandListener < BlankSlate
  def initialize
    @commands = []
  end

  def method_missing(*args)
    @commands << args unless [:inspect, :to_s].include? args.first 
    self
  end
  
  def pretty_print(pp)
    pp.output.write @commands.inspect
  end
    
end

listener = CommandListener.new

listener.instance_eval do
  You can even type freeze!
end
pp listener

And we get the following output:

[[:freeze!], [:type, #<CommandListener:0x7ee28>], [:even, #<CommandListener:0x7ee28>], [:can, #<CommandListener:0x7ee28>], [:You, #<CommandListener:0x7ee28>]]

On the same principals we just create a morse encoder, and of course Dave had to show off and interface with the speech function of OSX and another version that interfaces with the MIDI controller.

Exotic Control Flow

Creating a loop with continuations

def start_loop
  callcc{|c|c }
end

def end_loop(c)
  c.call(c)
end


i = 0
again = start_loop

  puts i
  i += 1

end_loop(again) unless i > 5

Moving on…

We voted on what to cover next as we won’t have time to cover every thing…and the winners are:

* Concurrency                  ..................
* Debugging/Profiling          ................
* JRuby                        ......
* Ruby Extras                  ...........
* Distributed Programming      ......................

Distributed Programming

DRb

Marshaling

>> h = {:x => 1}
>> Marshal.dump(h)
=> “\004\b{\006:\006xi\006”
>> Marshal.load(_)
=> {:x=>1}

DRB Server

require 'drb/drb'
require 'ostruct'

DRb.start_service("druby://localhost:4321", OpenStruct.new)
DRb.thread.join

DRb Client

require ‘drb’

DRB.start_service
o = DRbOject.new_with_url("druby:''localhost:4321")
o.last_accessed = Time.now
o.some_other_arbitrary_method = "Set this on the open struct"

By default Pass-by-value, but can be Pass-by-reference can be enabled by including DRbUndumped.

• Rinda
• Ring

…

That’s all Folk! …my hands/brain where running tired during the last hour :-)

That was an incredible 3 days thanks to Chad and Dave. So if you want to dive deeper in Ruby, the Advanced Ruby is the best way to get there!

Enjoy!
Daniel

 
1.class.ancestors
=> [Fixnum, Integer, Numeric, Comparable, Object, Kernel, BasicObject]

1.class.instance_methods(false)
=> [:to_s, :-@, :+, :-, :*, :/, :div, :%, :modulo, :divmod, :fdiv, :**, :abs, :magnitude, :==, :<=>, :>, :>=, :<, :<=, :~, :&, :|, :^, :[], :<<, :>>, :to_f, :size, :zero?, :odd?, :even?, :succ]

m = 1.method(:inspect)
=> #<Method: Fixnum(Kernel)#inspect>

...make it fast.

Benchmarking

require 'benchmark'
puts Benchmark.measure {(1..1000000).map{|num| ""+num.to_s}}
  0.940000   0.050000   0.990000 (  1.001714)

puts Benchmark.measure {(1..1000000).map{|num| ""+num.to_s}}
  1.800000   0.050000   1.850000 (  1.850319)

require 'benchmark'
Benchmark.bm do |b|
  b.report("map") {(1..1000000).map{|num| ""+num.to_s}}
  b.report("inject") {(1..1000000).inject(""){|accum, num| ""+num.to_s}}
end
      user     system      total        real
map  1.970000   0.070000   2.040000 (  2.077786)
inject  1.910000   0.010000   1.920000 (  1.978541)

Don't Use Ruby

require 'dl/import'
require 'dl/struct'

memoization

def fib(n)
 @k||={}
 n<=2 ? 1 : (@k[n-1]||=fib(n-1))+(@k[n-2]||=fib(n-2))
end

puts fib(200)
280571172992510140037611932413038677189525

Program exited with code #0 after 0.02 seconds

def fib(n)
  if n <= 2 
      1
  else
     fib(n-1) + fib(n-2)
  end
end

alias :pre_memoized_fib :fib

def fib(n)
  @cache ||= {}
  @cache[n] ||= pre_memoized_fib(n)
end

The Ruby Object Model

class << str   # << opens up the singleton class. Arrows seem to go wrong way.
  p self  # ghost class: <Class:#<String:0x1d0ec>> - class of the class String
  def speak
    puts "miaow"
  end
end

puts str.speak

class Dave
  class << self   # puts the methods into the singleton class and becomes class methods
    def do_something      
    end
  end
end

class Person < Struct.new(:name, :age)
  def greet
      puts "Hello #{self.name}"
  end
end

f = Person.new("Chad", 28)

module Logger
  def log(msg)
    puts msg
  end
end

class Album
  include Logger
end


Album.ancestors # => [Album, Logger, Object, Kernel]
# Note that Logger becomes ancestor of Album...It's insert a generated class named after the module that shares the method table.

module Speak
  def hello
     puts "hello"
  end
end

str = "cat"
str.extend Speak

puts str.hello

Metaprogramming

Library Organization