What an expert and deep-rooted C# developer discover about Ruby. Here are the impressions, the oddities and the WOWs.

1. RUBY SEEN BY A C#
DEVELOPER
Emanuele DelBono - @emadb

9. I AM
I am a software
engineer and web
architect in
CodicePlastico. I write
web apps in C#,
javascript e ruby.

10. IT ISN’T A RUBY TUTORIAL
!
It’s a bunch of stuff that made me say
WOW!

11. C# (2002)
!
• Compiled, strongly typed
• OOP (multiparadigm)
• Delegate/lambda/enumerators
• ECMA standard
• Mono on Linux and MacOS
• “A better java”

12. RUBY (1995)
• Dynamic
• Open Source
• Interpreted
• Multi inheritance through Mixin
• Fully OOP

13. HELLO WORLD
using System;!
public class Program
{!
public void Main()
{!
Console.WriteLine("Hello World");
}!
}!

14. HELLO WORLD
p 'hello world'

16. RAILS
class Employee < ActiveRecord::Base!
belongs_to :company!
attr_accessible :name, :surname, :role!
has_many :activities!
before_save :update_role!
scope :managers, -> { where(role: 'manager') }!
!
def update_role!
# ...!
end!
def foo!
# ...!
end !
end

17. ALL CODE IS EXECUTED
class MyClass < (rand < 0.5 ? Array : Hash)!
end!

18. WOW!

19. REAL OOP
class is an instance of class

20. class Cat
end
cat = Cat.new
puts cat
#<Cat:0x007fa2bc13d5d8>
puts cat.class
Cat
puts cat.class.class
Class
puts cat.class.class.class
!
Class

21. Klazz = Class.new
=> Klazz
puts Klazz
=> Klazz
puts Klazz.class
Class
k = Klazz.new
=> #<Klazz:0x007f8fc121ab58>

22. Foo = Class.new do
def bar
"I'm bar...an instance method of foo"
end
end
!
a = Foo.new
p a.bar
=> "hello"

23. WOW!

24. SINGLETON METHODS
We can add methods to a single instance

25. class Cat
def meow; ’meow’; end
end
cat = Cat.new
new_cat = Cat.new
def cat.argh
'argh'
end
p cat.meow
=> "meow"
p cat.argh
=> "argh"
p new_cat.argh
NoMethodError: undefined method `argh' for
#<Cat:0x007fda63085878>

26. ?
EIGENCLASS

27. THE OBJECT MODEL
• Every object, classes included, has its
own “real class,” be it a regular class
or an eigenclass
• The superclass of the eigenclass is the
object class
• The superclass of the eigenclass of a
class is the eigenclass of the class’s
superclass

28. THE OBJECT MODEL
class C; end
class D < C; end
obj = D.new
#Object
C
#C
D
obj
Object
#D
#obj
Metaprogramming Ruby - Pag. 125

29. WOW!

30. monkey patching
“a way to extend or modify the runtime
code of dynamic languages [...] without
altering the original source code.”

31. class String
def foo
to_s + ' fooed'
end
end
s = "hello"
puts s.foo
=> "hello fooed"

32. REMOVE METHODS
class String
remove_method :to_s
end

33. WOW!

34. duck typing
When I see a bird that walks like a duck
and swims like a duck and quacks like a
duck, I call that bird a duck
http://en.wikipedia.org/wiki/Duck_typing

35. class Type1
def foo; "I'm type1"; end
end
!
class Type2
def foo; "I'm type2"; end
end
def get_class
rand < 0.5 ? Type1 : Type2
end
!t
= get_class.new
p t.foo
=> "I'm type2" #or I'm type1

36. METHOD INTERCEPTION
Using alias and monkey patching we can
run through the execution

37. class
def
p
end
end
cat =
Cat
meow
"meow"
Cat.new
Cat.class_eval do
alias :meow_new :meow
def meow
p "i'm about to meow"
meow_new
p "did you hear me?"
end
end
=> "i'm about to meow"
=> "meow"
cat.meow
=> "did you hear me?"

38. METAPROGRAMMING
Metaprogramming is the writing of
computer programs that write or
manipulate other programs (or
themselves) as their data […]
http://en.wikipedia.org/wiki/Metaprogramming

39. METHOD MISSING
class Cat
def method_missing(method, *args)
#do something without failing
end
end

40. class Settings
def initialize(options)
options.each do |key, value|
self.instance_variable_set "@#{key}", value
self.class.send :define_method, key,
proc{self.instance_variable_get("@#{key}")}
self.class.send :define_method, "#{key}=",
proc{|v| self.instance_variable_set("@#{key}", v)}
end
end
end
c = Settings.new YAML.load_file("config.yaml")
!
p c.title # => "metaprogramming ruby"
p c.author # => "Paolo Perrotta"
p c.pub_year # => "2010"
!
c.title = 'metaprogramming ruby 2.00’
p c.title # => "metaprogramming ruby 2.00”

41. HOOKS
Since all code is executed. You can
intercept some “facts” about it.
inherited, append_features, included,
extend_object, extended, initialize_copy,
const_missing

42. WOW!

43. BUT THERE’S MORE
> [1, 2, 3] * 3 == [1, 2, 3, 1, 2, 3, 1, 2, 3]
> 1_000_000
> a = a || []
> a = [1,2,3]; a[-1]
> [1,2,3].shuffle
> (0..9).each { ... }
> 3.times {...}
> def name=(value); ...

44. PHILOSOPHY
I hope to see Ruby help
every programmer in the
world to be productive, and
to enjoy programming, and
to be happy. That is the
primary purpose of Ruby
language.
Yukihiro
Matsumoto

45. o = Object.new!
o.methods.count
=> 54
• ActiveRecord::Base => 367
• String => 161
• Fixnum => 128

46. SAME METRICS?
DIFFERENT WORLD?

47. RUBY PRO
• Simplicity
• REPL (irb, rails c, heroku run console)
• No ceremony
• One file app
• Community and frameworks
• Expressiveness (DSL)

48. CONS
• Freedom bring responsibility
• Performance
• No tools for refactoring
• Tests are mandatory (mmh…)

49. DOES IT WORTH?

50. LINGUISTIC RELATIVITY
“The principle of linguistic relativity holds
that the structure of a language affects
the ways in which its respective speakers
conceptualize their world.”
Sapir–Whorf hypothesis
http://en.wikipedia.org/wiki/Linguistic_relativity

51. THE PRAGMATIC
PROGRAMMER
“Learn at least one new language every
year. Different languages solve the same
problems in different ways. By learning
several different approaches, you can
help broaden your thinking and avoid
getting stuck in a rut.”
The Pragmatic Programmer

52. MORE LANGUAGES
==
BETTER PROGRAMMER