Dreaming of a Ruby Christmas

This Week’s Ruby Quiz is to create something creative XMas related in Ruby. Glen F. Pankow came with the following solution:

You can check out / download the code from here – which btw prints the following poem:

On the first day of Matzmas my true love gave to me:
   A new version of Ruby!

On the second day of Matzmas my true love gave to me:
   Two string gsubs
   And a new version of Ruby!

On the third day of Matzmas my true love gave to me:
   Three forked threads
   Two string gsubs
   And a new version of Ruby!

On the fourth day of Matzmas my true love gave to me:
   Four calling procs
   Three forked threads
   Two string gsubs
   And a new version of Ruby!

On the fifth day of Matzmas my true love gave to me:
   Five Ruby gems!
   Four calling procs
   Three forked threads
   Two string gsubs
   And a new version of Ruby!

On the sixth day of Matzmas my true love gave to me:
   Six marshals dumping
   Five Ruby gems!
   Four calling procs
   Three forked threads
   Two string gsubs
   And a new version of Ruby!

On the seventh day of Matzmas my true love gave to me:
   Seven ducks a-typing
   Six marshals dumping
   Five Ruby gems!
   Four calling procs
   Three forked threads
   Two string gsubs
   And a new version of Ruby!

On the eighth day of Matzmas my true love gave to me:
   Eight dirs a-globbing
   Seven ducks a-typing
   Six marshals dumping
   Five Ruby gems!
   Four calling procs
   Three forked threads
   Two string gsubs
   And a new version of Ruby!

On the ninth day of Matzmas my true love gave to me:
   Nine ranges stepping
   Eight dirs a-globbing
   Seven ducks a-typing
   Six marshals dumping
   Five Ruby gems!
   Four calling procs
   Three forked threads
   Two string gsubs
   And a new version of Ruby!

On the tenth day of Matzmas my true love gave to me:
   Ten trys a-catching
   Nine ranges stepping
   Eight dirs a-globbing
   Seven ducks a-typing
   Six marshals dumping
   Five Ruby gems!
   Four calling procs
   Three forked threads
   Two string gsubs
   And a new version of Ruby!

On the eleventh day of Matzmas my true love gave to me:
   Eleven ios piping
   Ten trys a-catching
   Nine ranges stepping
   Eight dirs a-globbing
   Seven ducks a-typing
   Six marshals dumping
   Five Ruby gems!
   Four calling procs
   Three forked threads
   Two string gsubs
   And a new version of Ruby!

On the twelveth day of Matzmas my true love gave to me:
   Twelve monkeys patching
   Eleven ios piping
   Ten trys a-catching
   Nine ranges stepping
   Eight dirs a-globbing
   Seven ducks a-typing
   Six marshals dumping
   Five Ruby gems!
   Four calling procs
   Three forked threads
   Two string gsubs
   And a new version of Ruby!

Hats down before this solution, I really bow down to Glen’s creativity and technique – the only problem is that I find the bar too high (and the time is too little) to submit a solution this time :-).

Anyway, happy XMas time everyone!

AJAX Scraping with scRUBYt! – LinkedIn, Google Analytics, Yahoo Suggestions

scrubyt-logo-transparent.png As announced on the scRUBYt! blog, there is a brand new release of scRUBYt!, (among other additions) enabling AJAX scraping. I’d like to present a few examples of kicking the data out of non-trivial-to-scrape pages: LinkedIn, Google Analytics and Yahoo (which in itself is not a big deal – unless you want to scrape the suggestions that pop up after entering a keyword into the search text field).

Without further ado, let’s get down to business!


Let’s say you’d like to scrape your LinkedIn contact list – first name, last name and e-mail of every contact you have. What makes this task complicated (but not for scRUBYt!) is that the contact list is inserted with AJAX after the page is loaded into the browser, and thus it is ‘invisible’ to a standard HTML parser like Hpricot/Nokogiri, so don’t try with those. Instead, check out how you might do it with scRUBYt!:

property_data = Scrubyt::Extractor.define :agent => :firefox do
  fetch          'https://www.linkedin.com/secure/login'
  fill_textfield 'session_key', '*****'
  fill_textfield 'session_password', '*****'

  click_link_and_wait 'Connections', 5

  vcard "//li[@class='vcard']" do
    first_name  "//span[@class='given-name']"
    second_name "//span[@class='family-name']"
    email       "//a[@class='email']"

puts property_data.to_xml

Result: for the above records:


is the following:

    *** alex's email ***
    *** peter's e-mail ***
    *** jim's e-mail***

The magick is happening on line 7: you click the ‘Connections’ link and wait 5 seconds, until the list is loaded with AJAX. Then you can scrape the contacts as you would do normally.

Frames won’t stop us – Google Analytics

Besides being AJAXy, google analytics throws some more complexity into the mix: The login fields are in a frame, which is again not trivial to scrape – fortunately scRUBYt! abstracts all that frame handling away and makes this really easy:

data = Scrubyt::Extractor.define :agent => :firefox do
  fetch 'https://www.google.com/analytics/reporting/login'
  frame :name, "login"

  fill_textfield 'Email', '*****'
  fill_textfield 'Passwd', '*****'
  submit_and_wait 5

  pageviews "//div[@id='PageviewsSummary']//li[@class='item_value']", :example_type => :xpath

puts data.to_xml

All you had to do is to ‘go into’ the frame named login. It looks like any navigation step (and basically we can consider it one) after which the scraping is executed on the document in the frame.
We again used an _and_wait method – it takes some time until everything is loaded after logging in.

Scaping an AJAX pop-up

Technically this is not much different from the first scenario, but it’s interesting nevertheless. The task is to scrape the suggestions that yahoo pops up after you enter something into the search field:


Here is the scraper:

require 'rubygems'
require 'scrubyt'
require 'cgi'

Scrubyt.logger = Scrubyt::Logger.new

yahoo_data = Scrubyt::Extractor.define :agent => :firefox do
  fetch 'http://www.yahoo.com'
  fill_textfield_and_wait 'p', 'ruby', 5

  suggestion_list "//div[@id='ac_container']//li/a", :example_type => :xpath do
    href "href", :type => :attribute do
      escaped_string /&p=(.+?)$/ do
        suggestion lambda {|x| CGI::unescape(x)}, :type => :script

p yahoo_data.to_hash

The result:

[{:suggestion=>"ruby tuesday"}, 
 {:suggestion=>"pokemon ruby"},
 {:suggestion=>"ruby bridges"},
 {:suggestion=>"max and ruby"},
 {:suggestion=>"ruby falls"},
 {:suggestion=>"ruby rippey tourk"}, 
 {:suggestion=>"ruby lane"},
 {:suggestion=>"pokemon ruby cheats"},
 {:suggestion=>"ruby skye"},
 {:suggestion=>"ruby lin"}]

You can download the above (and other) examples from the scRUBYt! examples github repository:

git clone git://github.com/scrubber/scrubyt_examples.git

Please check out scRUBYt’s homepage for more info!

Ruby Quiz – Mix and Match

Solved another Ruby Quiz:

I purchased a number of scented candles recently for sending out to friends and family. While I could be accused of being lazy by getting candles for several people, I’d like to mix up the candles a bit so that each recipient gets a different combination of scents.

Please help me out! Your task is to write a method that randomizes and mixes up the individual candles into groups, one per recipient, in order to minimize group duplication. So, for example:

candles = { :orange   => 3,
            :vanilla  => 2,
            :lavender => 2,
            :garden   => 4 }

recipients = %w(janet nancy susan)

candles_per_recipient = 3

mix_and_match(candles, recipients, candles_per_recipient)

=> { "janet" => [:garden, :lavender, :orange],
     "nancy" => [:garden, :orange, :vanilla],
     "susan" => [:garden, :lavender, :vanilla],
     :extra  => { :orange   => 1,
                  :vanilla  => 0,
                  :lavender => 0,
                  :garden   => 1

If it is impossible to have a unique combination for every recipient, you should still generate some set of combinations, minimizing repetition of combinations.

If the number of recipients times the number of candles per recipient is more than the supply, generate an error.

Proposed solution: (for the impatient, the source code is here.) In my interpretation, this is a simple combinatorial problem: say the number of recipients is r and candles\_per\_recipient is c, then you are looking for a (preferably non-repeating) random selection of r elements of c-combinations of the original set of candles. (In fact it’s a bit more complicated than that: the c-combinations have to be recalculated from the remaining candles each time you give away a group of candles, so we’ll get to that). Sounds confusing? Don’t worry, after the implementation everything will be clear!

So first, define a k-combination for a histogram (a Hash like candles above, where keys are elements and values are cardinalities):

class Hash
  def comb(group_size)
    result = []    
    inner_comb = lambda do |head,tail|
      tail[0..-(group_size-head.size)].each do |e|
        if (head.size >= group_size-1)
          tail.each {|t| result << head + [t]}
          inner_comb[head + [e], tail[tail.index(e)+1..-1]] 
    inner_comb[[],self.inject([]) {|a,v| v[1].times{a << v[0]}; a}]


candles = { :orange   => 2,
            :vanilla  => 1,
            :lavender => 1, 
            :garden => 1 }
pp candles.comb(3)

=> [[:lavender, :garden, :orange],
    [:lavender, :garden, :vanilla],
    [:lavender, :orange, :orange],
    [:lavender, :orange, :vanilla],
    [:garden, :orange, :orange],
    [:garden, :orange, :vanilla],
    [:orange, :orange, :vanilla]]

so for a set of candles, this method generates all possible 3-combinations of the candles. We can then pick one and assign it to one of the recipients. Then recalculate the above from the remaining candles, give it to the next recipient - and so on and so forth. That's the basic idea, but we also need to ensure the candle combinations are as non-repeating as possible. So let's define some further utility methods:

class Hash
  def remove_set(set)
    set.each {|e| self[e] -= 1}

The above code adjusts the number of candles in the original hash once we give away some of them. So for example:

candles = { :orange   => 2,
            :vanilla  => 1,
            :lavender => 1, 
            :garden => 1 }
p candles
=> {:lavender=>0, :garden=>1, :orange=>0, :vanilla=>1}

and some Array extensions:

class Array 
  def rand
    uniqs = self.select{|e| e.uniq.size == e.size}
  uniqs.empty? ? self[Kernel.rand(length)] : uniqs[Kernel.rand(uniqs.length)]
  def unordered_include?(other)
    self.map{|e| e.map{|s| s.to_s}.sort}.include? other.map{|s| s.to_s}.sort

Array#rand is trying to pick a random non-repeating combination if there is one (so e.g. [:orange, :lavender, :garden]) or, if there is no such combination, then just a random one (e.g. [:orange, :orange, :garden] - orange is repeating, but we have no other choice).

Array#unordered_include? is like normal Array#include?, but disregards the ordering of the elements. So for example:

  [[:lavender, :garden, :orange]].include? [:lavender, :orange, :garden] => false
  [[:lavender, :garden, :orange]].unordered_include? [:lavender, :orange, :garden] => true

Hmm... it would have been much more effective to use a set here rather than the above CPU-sucker, but now I am lazy to change it 😉

OK, so finally for the solution:

ERROR_STRING = "The number of recipients times the number of candles per recipient is more than the supply!"

def mix_and_match(candles, recipients, candles_per_recipient)
  return ERROR_STRING if ((candles.values.inject{|a,v| a+v}) < (recipients.size * candles_per_recipient))
  candle_set = recipients.inject({}) do |a,v|
    tried = []
    tries = 0
    loop do
      random_pick = candles.comb(candles_per_recipient).rand
      tried << random_pick unless tried.unordered_include? random_pick
      break unless a.values.unordered_include? random_pick
      break if (tries+=1) > candles.values.size * 2
    a[v] = tried.last
  candle_set.merge({:extra => candles})

So, in the inner loop we randomly pick a candles-per-recipient-combination of all the possible combinations; If no one has that combo yet, we assign it to the next recipient. If someone has it already, we try to find an unique combination (loop on), unless it is impossible (checked on line #12). In this case we simply start giving out any combinations. Once we give away a set of candles, we remove them from the original set. Easy-peasy.

You can check out the source code here.

This was a great quiz, too bad that not many people took a stab at it (so far 1 except me ;-)). The hardest part for me was the implementation of the k-combination (and the result looks awful to me - I didn't check any algorithm/pseudocode/other solution though, I wanted to roll my own) - after that the problem was pretty simple. Cheers for the Ruby Quiz guys (== ["Matthew Moss"] I guess?) for this quiz.

Add a powerful AJAX Table to your Rails Application in 5 minutes

I needed to add an AJAX grid/table component with all the bells and whistles (AJAX sorting, pagination, multiple row select, AJAX add/delete etc) to an application I am working on right now (will blog about it when we roll out a good-enough version). We are using jQuery so I started looking for a suitable plugin.

I believe I have found it – it’s called jqGrid and it’s super sexy, feature rich and the documentation is on par with a commercial tool – so I created a Rails plug-in enabling you to add it to your Rails app in no time! Follow the 10 steps below to find out how.

  1. Create a blank Rails app (in your home dir – or change the path in the next step):
    rails -d mysql grid_test
  2. install jQuery:
    curl http://jqueryjs.googlecode.com/files/jquery-1.2.6.pack.js > ~/grid_test/public/javascripts/jquery.js
  3. install jquery\_grid\_for_rails – I am using giternal (how to install), so this is what you need to do in this case:
    open config/giternal.yml and enter:

      repo: git://github.com/scrubber/jquery_grid_for_rails.git
      path: vendor/plugins

    then run

    giternal update

    (obviously you can use script/plugin, git submodules, piston, braid or whatever floats your boat)

  4. Generate a migration to test out stuff with:

    script/generate resource person
    class CreatePeople < ActiveRecord::Migration
      def self.up
        create_table :people do |t|
          t.string :first_name, :last_name, :title, :i_can_has_cheezburger 
      def self.down
        drop_table :people
  5. generate dummy data

    script/generate migration create_dummy_people_data_migration
    class CreateDummyPeopleDataMigration < ActiveRecord::Migration
      def self.up
        Person.create :first_name =>"He", :last_name => "Man", :title => "Hero", :i_can_has_cheezburger => "Sure"
        Person.create :first_name =>"Bat", :last_name => "Man", :title => "Mr.", :i_can_has_cheezburger => "Yeah"
        Person.create :first_name =>"Cat", :last_name => "Woman", :title => "Ms.", :i_can_has_cheezburger => "Yes"
        Person.create :first_name => "Super", :last_name => "Man", :title => "d00d", :i_can_has_cheezburger => "Nope"
        Person.create :first_name => "Spider", :last_name => "Man", :title => "Mr.", :i_can_has_cheezburger => "Meh"
        Person.create :first_name => "Chuck", :last_name => "Norris", :title => "Sir", :i_can_has_cheezburger => "Who is asking?"
        Person.create :first_name => "G.I.", :last_name => "Joe", :title => "Sgt", :i_can_has_cheezburger => "What is a cheezeburger?"
      def self.down
  6. Time to run the migrations!

    Set up the db first:

    rake db:create

    run teh migrations:

    rake db:migrate
  7. Set up the controller (PeopleController) - add this method:

      def grid_data
        @people = Person.all(:order => "#{params[:sidx]} #{params[:sord]}")
        respond_to do |format|
          format.xml { render :partial => 'grid_data.xml.builder', :layout => false }
  8. Modify config/routes.rb to look like

    map.resources :people, :collection => {:grid_data => :get}
  9. This goes into your application layout (create a new file - views/layouts/application.html.erb):

    		jqGrid Test App - w00t!
    		<%= javascript_include_tag 'jquery' %>
    		<%= include_jquery_grid_javascript %>
    		<%= include_jquery_grid_css %>
    		<%= yield %>
  10. The last step: views (views/people/_grid_data.xml.builder, views/people/index.html.erb)

    xml.instruct! :xml, :version=>"1.0", :encoding=>"UTF-8"
    xml.rows do
      xml.page params[:page]
      xml.total_pages (@people.size.to_i / params[:rows].to_i)
      @people.each do |u|
        xml.row :id => u.id do
          xml.cell u.title
          xml.cell u.first_name
          xml.cell u.last_name
          xml.cell u.i_can_has_cheezburger
      <%= jquery_grid :sample, {:url => grid_data_people_url } %>
    My cool AJAX grid!
    <%= jquery_grid_table %> <%= jquery_grid_pager %>
  11. That's it! Start script/server, point your app to http://localhost:3000/people and if you did everything according the tutorial, you should (hopefully) see something like this:


    I have uploaded the app to github, be sure to check it out (WARNING - don't copy and paste from the above code, the code highlighting plugin has some problems and you'd get strange results. Clone the repo instead).

    Note that the installed plug-in is included in .gitignore so you have to run "giternal update" after you clone it.

    Drop me a comment if you experience any problems!

Thinking About Switching to jQuery?

jquery.pngI was pondering the question too – fortunately not for long! I am in the jQuery camp now and couldn’t be happier about it. Now, I am not saying it is for everyone, neither that it is superior to prototype / script.aculo.us or anything like that (neither with nor without Rails) – all I am saying is that I switched and didn’t regret it! As my earlier research based on Rails Rumble suggested, more and more people are switching to jQuery (as well as companies like Microsoft and Nokia), so why couldn’t you give it a spin? Here are some articles and stuff I found useful when I was in your shoes:

What’s the Great Idea?!

Coming from Prototype? Who isn’t…

Going Further



  • jQuery in action – I am reading this book at the moment and it totally kicks ass.

What are you waiting for? Enter the red tower of Hanoi – you won’t be disappointed!

Simple Ideas, Great Usability

Sometimes even the simplest things can bring a big boost in usability. A small sampler I came across recently:

letsfreckle.com: clear text password field – which you can of course turn into a regular one by checking a checkbox in case someone is standing behind your back with the intention of stealing your future freckle password (only God knows what could happen then)! Beware of the (web 2.0) ninjas though, they can hide pretty well – so be sure to turn on the password hiding if you are sitting in a black room!


omgbloglol.com: If you comment on an article, you can check a checkbox stating that you’d like to receive an e-mail if anyone makes a new comment. I’d like to have this everywhere (yeah I know about services like www.cocomment.com and co.mments.com but I found them clumsy compared to the above solution)


news.ycombinator.com: Simplest. Signup Form. Ever.


It would be great if other sites would realize that you don’t necessarily need your mom’s maiden name and similar info to sign up – it’s perfectly ok to supply that later on.

It’s That Time of the Year Again: Ruby Advent 2008

Lakshan Perera, a Ruby developer from Sri Lanka started a new project for the holiday season: Ruby Advent Calendar (although it’s not uniquely new – you might remember Ruby Inside’s Advent 2006). I am really happy to see this project – I learned a lot about Ruby with the Ruby Inside advent calendar too.

Lakshan is looking for contributors (check it out here) so if you have an interesting Ruby trick (or two) you’d like to share (intended audience: beginners to intermediate developers), contact him via the blog entry. There is a low traffic (1/day for the next 24-3 days) twitter feed you can subscribe to.

Happy Ruby Advent 2008 everyone 🙂

Hot in Edge Rails: Generate Rails Apps from Templates

Update: Pratik covers rails templates in more detail here.

I hate to use uber-superlatives, but this is just plain frakkin awesome to the power of a Chuck Norris roundhouse-kick: Jeremy McAnally‘s rg (don’t worry if you have no clue about rg – I heard about it 10 minutes ago myself (via Pratik)) made it to the rails core.

So what the hell is rg to begin with? rg is a rails generator, like the ‘rails’ command (the one used to create a blank Rails app) just way cooler. You think it has never been easier to create a skeleton app because we have bort? Well, then check this out:

(Eyes glazing over? Check it out (as well as other examples) on github).

It’s hard to believe, but the above template is able to generate a clean rails app which is basically bort (Or exactly bort. Or very similar to bort. Or similar to a bort lookalike. Or… I guess I leave this debate up to ruby lawyers, bort experts, rg zealots etc.) Anyway, it doesn’t really matter as rg was not invented to compete with bort – bort is merely used as an example because it’s probably the most popular Rails skeleton app nowadays – rg is far more general than that: an easy, concise, Rubyish way to describe your Rails app (including plugins, vendored gems, lib files, initializers and whatnot) in a very straightforward way.

There are a handful of base Rails apps out there – but the chance that one of them is *exactly* using the tools you are committed to is minimal. For example I prefer HAML to erb, SASS to CSS, jQuery to Prototype, somewhat undecided between Shoulda and rSpec, I’d like to give authlogic a spin the next time I need user authentication etc. and the list goes on and on – and it changes over time. With this addition to Rails this is no problem – it takes minutes to cook your own Rails skeleton app, and minutes to adjust it later.

If this is still not enough, check out the Jeremy’s TODO list: Save yourself the hassle of keeping your core components up to date (coming soon). OMG, I have been waiting for something like this for ages, and I doubt I am alone (though the ability to describe gems in environment.rb was a great leap forward) – this will really rock! Kudos Jeremy!

Forget Rock Stars, Gurus, Ninjas and Zen Masters

I thought it’s impossible to significantly enhance this collection, at least with something similarly cyber-h4xx0r-zen-ninja-ish. Well, I am not so sure any more (via linkedin):


Maybe with the Web2.0 bust (?), popular clichés for uber-giga-great developers are fading out too – indeed, who needs an old-fashioned web2.0 ninja (even if he’s a pirate in his free time) if you can hire a Web2.5 code terrorist to…. umm… get some coding done?!?

Update: The article was featured on hacker news and now it’s clear that Giles’s original article can be significantly extended, for example with:

  • Python 3000 Jihadists
  • JavaScript Martyrs
  • Ruby Bionic Commando
  • Rails Black Magicians

and others… check out hacker news if this is still not enough inspiration for you!

Decorating Instance Methods of a Class

I am just working on a brand new release of scRUBYt!, with the intent of bringing AJAX/javascript scraping to the masses (and other great stuff – will announce the release soon).

Scraping js-heavy pages is not that trivial, among other things because of the asynchronous nature of Javascript. Quite frequently you click on a link (or do any other action triggering an AJAX call) which inserts/fills/pops up a div on the page and you want to navigate/get some data from the new content. However, it’s hard to impossible to determine when did the browser finish displaying the new data – the easiest solution is to wait a few seconds after an AJAX update, until the data is properly loaded.

In practice this means that all scRUBYt! navigation methods (click_link, fill_textfield, check_checkbox, select_item, …) need a decorated version, which waits a given amount of time after executing the navigation step. So for example, given the original method:

def click_link(xpath) ... end

we want a decorated version:

def click_link_and_wait(xpath, seconds)
  click_link xpath #the original method
  sleep seconds if seconds > 0

For each and every method of the NavigationAction class.

Fortunately Ruby makes this really easy! Decorating the existing methods explicitly upon class creation:

  (instance_methods - Object.instance_methods).each do |old_method|
    define_method "#{old_method}_and_wait" do |seconds|
      send old_method ; sleep seconds

or implicitly, runtime:

alias_method :throw_method_missing, :method_missing

def method_missing(method_name, *args, &block)
  original_method_name = method_name.to_s[/(.+)_and_wait/,1]
  if (method_name.to_s =~ /_and_wait/) && (respond_to? original_method_name)
    self.send original_method_name ; sleep args[0]
    throw_method_missing(method_name, *args, &block)

As you can see, we are executing the decorated method only if it is defined on our class and it ends in _and_wait. In all other cases we simulate the normal method_missing_behavior.

Since we know in advance that we want to decorate all the methods of the class, the second way doesn’t make much sense in this case – it’s slower because it has to go through method_missing every time, while there are no advantages – however the technique is interesting and applicable in other scenarios (e.g. when you don’t know in advance which methods are you going to decorate – for example adding a constraint to a filter in scRUBYt! (filters are also created dynamically runtime))

Git External Dependency Management with Giternal

I Don’t want to reiterate what has already been said on this topic (I ended up in the same boat – tried more tools, didn’t really like any of them and settled for giternal).

Giternal seems to work nicely – after you get the initial roadblock out of the way. According to the README, you should install giternal with

gem install giternal

then use the _giternal_ executable to do various things.

The problem is that after installation, there is no _giternal_ executable – the problem is that gem installs version 0.0.1, which doesn’t have it. You have to get the sources from git and set it up yourself:

git clone git://github.com/pat-maddox/giternal.git
cd giternal
sudo ruby setup.rb

and you are good to go.

Hope this saves someone a few minutes.

Ruby Quiz: Unit Conversions

ruby_quiz.png I decided to join Ruby Quiz for the first time ever – I am realizing that I am extremely late to jump on the RQ bandwagon – but hey, is still better later than never. I have chosen a funny moment though: it’s a quiz everyone was excited about, but almost nobody solved (2 solutions so far except mine, which is maybe the lowest number of solvers ever). So here’s the quiz:

Your task is to write a units converter script. The input to the
script must be three arguments: the quantity, the source units, and
the destination units. The first example above would be run like this:

    $ ruby convert.rb 50 miles kilometers

Or, using abbreviations:

    $ ruby convert.rb 50 mi km

Support as many units and categories of units (i.e. volume, length,
weight, etc.) as you can, along with appropriate abbreviations for
each unit.

and my solution:

require 'rubygems'
require 'cgi'
require 'scrubyt'

google_converter = Scrubyt::Extractor.define do
 fetch "http://www.google.com/search?q=#{CGI::escape(ARGV[0])}+#{CGI::escape(ARGV[1])}+to+#{CGI::escape(ARGV[2])}"

 google_result "//td[@dir='ltr']" do
   final_result(/= (.+) /)
 puts google_converter.to_hash[0][:final_result]
 puts "Sorry, even *google* can't translate that!"


ruby converter.rb 10 "meter per second" "mile per hour"

ruby converter.rb 10 USD EUR

ruby converter.rb 7 "ruby gems" "python eggs"
Sorry, even *google* can't translate that!

The biggest downside of the proposed solution is that you need to be on-line. However, nowadays, when this is almost the norm, the advantages outweigh this in my opinion:

  • Support for a lot of conversions (I doubt anyone can offer a much richer database of units than google) including their abbreviations
  • Up-to-date conversions: for example currency conversion
  • Very robust error handling – outsourced to google! Hard to beat that…

Why Buying a Mac for (Rails) Developers is a Good Idea

“It’s better to be a pirate than to join the Navy” (Steve Jobs)

This post was inspired by the last part of Jim Neath’s article on speeding up Rails development, titled “Seriously, Just Buy a Fucking Mac”. Some commenters insisted that you can do just as well on other systems (Ubuntu, in particular). In three short words, I don’t agree. In my opinion Ubuntu is a valid alternative but it comes in at second place, and the gap between the 1st and 2nd position is significant. Why?


Some people, when it comes to a good PC vs. Mac fight, start to brag about the hardware – it’s overpriced, and not that much better, and my high end PC notebook is better because … etc. Because they most probably never ever used a Mac for a longer period, they don’t know that the real speed gain/ease || joy of use comes from the software (though it doesn’t hurt that there are no hardware conflicts, evar, no matter how much do you upgrade, no messing around with wifi/mic/video cards/you name it and the quality is top-notch etc.) No. The real secret sauce is the software:

The essential stuff


Ruby and Rails – I have spent a few years on Ubuntu from warty to gutsy, and though it was improving from release to release, when I bought an MBP a year ago, the difference was shocking. C’mon, installing Ruby and the whole Rails stack on ubuntu is still a considerable pain, whereas OS X ships with ruby/rails by default.


A powerful editor – TextMate the best editor ever invented, hands down – mainly when beefed up with Ruby/Rails bundles (the ‘standard’ ones, as well as others like RubyAMP). No windows or linux editor comes even close – though this is hard to believe unless you tried TextMate for more than 5 minutes.
I have been drooling when I was on Ubuntu and checked out screencasts like peepcode Textmate 2 for rails – fortunately I bought a Mac, watched the video and using Textmate ever since, so the drooling stopped.


An intuitive SQL GUI – CocoaMySQL/Sequel Pro. Sorry guys, MyPHPAdmin doesn’t count. Neither does mysql-query-browser, which is the windows 3.11 of the SQL GUIs IMHO. Sequel Pro rocks!

Other niceties


Skitch is something I had no clue I needed, but now I couldn’t live without it! “Skitch.com is a webservice that works hand in hand with our application Skitch to give you 1-click
uploading of images for fast and fun image sharing.”
. Doesn’t sound that mind-numbing, but try it once and become addicted forever.


Dropbox is a kickass utility to store, sync and share your files online. The best part is that it actually works – it’s not some half-assed solution, but a really working, beautifully executed powerful tool for sharing your stuff.


Cyberduck is an an incredibly useful FTP, SFTP, WebDAV & Amazon S3 Browser for Mac OS X. Really missed something similar under Ubuntu.


CSSEdit – I was really missing a good CSS editor under Linux – the existing ones didn’t even come close to CSSEdit. CSSEdit’s intuitive approach to style sheets and powerful previewing features will make you deliver awesome standards-based sites in no time!


MarsEdit is a desktop blog editor, so you can write a blog without giving up the comforts of your Mac. Since I am using MarsEdit, blogging has become a whole new experience – instead of a clumsy web-interface which requires me to be on-line I can focus on blogging actually!

Once you get productive with these extremely powerful tools (and I didn’t even mention the standard built in stuff like Spotlight, iCal, iChat, Time Machine, …) your development time will be greatly reduced compared to that on an Ubuntu/Windows/… machine. For realz!

Everyone and Their Dog is on a Mac

So… why should I keep up with the Joneses – did the me-too club become popular recently? Isn’t Apple’s mantra ‘think different’? Why join the ‘cool kids’?

Valid questions – however, everyone else being on macs also means that

  • you’ll have a much bigger chance of getting quick support on the Ruby/Rails forums/IRC – which is not always easy with Ubuntu (I am on Ubuntu Rusty Robot build R2-D2. Everything is fine, but MySQL driver doesn’t compile because I ran dist-upgrade yesterday, and now everything is jammed. All the tutorials are up to Humpty-dumpty Drake only…).
  • Easier collaboration – sharing Dropbox folders, skitch images, iCal events etc. is very-very common – of course there are other ways of sharing data/notes/collaboratively editing documents, but these Mac tools take it to a whole new level.
  • Growing Mac usage means that more goodness is on the way!

A bit of Mythbusting

  • Macs are crazy expensive
  • You can buy a mac mini starting from $599, or a pre-owned one for $350. Doesn’t sound like bank-breaking. Good PCs are not cheap either – my last DELL was about the same price as my current (almost high-end) MBP. Of course you can buy an Acer for third of the price, but well, the drop in the quality will be proportional.

  • Mac software is expensive, on linux everything is free
  • From the above list, everything essential is free, except TextMate, which is a must, no matter how much it costs. Usually free alternatives exist for almost everything, and the commercial ones are just unbelievably good.

  • You are going to deploy to a linux server, so create your app on linux too
  • While OS X is not linux based, the difference is minimal – Darwin is a POSIX compliant OS so from the Rails development perspective it doesn’t really matter. I do not have accurate data but I don’t think so it’s easier to migrate an app developed on gentoo/fedora/suse/… to an ubuntu box than to do the same for an OS X Rails app. And even deploying from Ubuntu to Ubuntu can be a pain unless the boxes contain the same version of everything etc.

  • I think you just bought a Mac because the “cool kids” did
  • So what? Does this alter the fact that working on a Mac makes you more productive/effective as described above? Not at all.

Use the Best Tool for the Job

Yeah… in other words, seriously, just buy a fucking mac. It’s the best tool when it comes to (not only) Ruby/Rails development.