Introduction to Ruby programming language

1. Vilniaus Ruby bendruomenė
Ruby.new
Vidmantas Kabošis @ VilniusRB.new
2014-11-22

2. @vidmantas
twitter/github

4. Other companies (LT)

5. Worldwide companies

6. 1995

7. 2004

8. 2.1.5

9. 2.1.x

10. 2.x.x

11. x.x.x

12. Why?
Ruby is designed for
expressiveness & happiness
Open source, from the heart:
licensing, friction,
ecosystem1
1 - http://blog.codinghorror.com/why-ruby/

13. One of the many
Perl
C Java
PHP C#
Ruby Delphi
Objective-C
C++
Python
VB
Javascript
R
SQL
F#

14. One of the many interpreted
Perl
C Java
PHP C#
Ruby Delphi
Objective-C
C++
Python
VB
Javascript
R
SQL
F#

15. Ruby
Interpreted
Dynamic
Object-oriented
General purpose

16. Types
Dynamically but strongly typed
0 == "0"

17. Types
Dynamically but strongly typed
0 == "0".to_i

18. Vilniaus Ruby bendruomenė
describe "WiFi" do
ssid "ruby"
password "vilnius"
end

19. More warmup examples
"vilniusrb".length
[1, 2, 3].include?(3)
"vilniusrb".include?("rb")
print "YOLO" if 1 > 2
2 * 2 + 2

20. Method definition
def hello
puts "Hello Ruby"
end

21. Calling the method
hello

22. Calling the method
hello
Hello Ruby

23. Calling the method
hello()
Hello Ruby

24. Method with parameter
def hello(name)
puts "Hello #{name}"
end

25. Calling the method & param
hello("PHP")
Hello PHP

26. Method with default param
def hello(name = "Ruby")
puts "Hello #{name}"
end

27. Calling the method & param
hello
Hello Ruby

28. Calling the method & param
hello ".NET"
Hello .NET

29. Flow control: if
if [1, "rb", nil].count >= 3
world_peace
else
depression_with_chocolate
end

30. The truth & the lies
false
nil

31. Check the truth
[]
0

32. Iteration
s = "Vilnius Ruby
community".split

33. Iteration
s = [
"Vilnius",
"Ruby",
"community"
]

34. Iteration: the classics
for (i = 0; i < s.length; i++) {
// do something with s[i]
}

35. Iteration: the Ruby way
s.each do |word|
# do something with word
puts word.upcase
end

36. Blocks
s.each do |word|
# do something with word
puts word.upcase
end

37. Blocks: implementation
def each
size.times do |i|
yield(self[i])
end
end

38. Blocks: implementation
def each
size.times { |i| yield(self[i]) }
end

39. Blocks: implementation
def each(&block)
size.times do |i|
block.call(self[i])
end
end

40. Enumerable
.map .max
.inject .min
.reject .partition
.all? .select
.any? .sort
.detect .first

41. Enumerable in action
[10, 5, 7]
.map { |n| n * 2 }
.select { |n| n > 10 }
.sort
.first

42. Enumerable in action
[10, 5, 7]
.map { |n| n * 2 } # [20, 10, 14]
.select { |n| n > 10 } # [20, 14]
.sort # [14, 20]
.first # 14

43. Objects
Everything
is an object

44. Really
*Everything*

45. Classes are instructions

46. Objects - real instances

47. Classes are instructions
class Phone
def initialize(name)
@name = name
end
def bends?
@name == :iphone
end
end

48. Objects - real instances
iphone = Phone.new(:iphone)
iphone.bends? # true
nokia = Phone.new(:3310)
nokia.bends? # false

49. It’s about time for magic!

50. Classes are always open
class String
def last_capitalize
reverse.capitalize.reverse
end
end

51. Classes are always open
class String
def last_capitalize
reverse.capitalize.reverse
end
end
"vilniusrb".last_capitalize
"vilniusrB"

52. Define methods, everywhere
vrb = "vilniusrb"
def vrb.rb_capitalize
gsub("rb", "RB")
end
vrb.rb_capitalize
"vilniusRB"

53. Missing a method?
class Phone
def method_missing(mname, *args, &block)
puts "I don’t know about `#{mname}`"
puts caller.first
end
end

54. Missing a method?
def method_missing(mname, *args, &block)
puts "I don’t know about `#{mname}`"
puts caller.first
end
Phone.new.flips?
I don’t know about `flips?`
/my/file/path/phone.rb:42:in `<main>`

55. Who’s who?
ccllaassss Phone
def initialize(&block)
instance_eval(&block)
end
def answer!
puts "Howdy?"
end
end

56. Who’s who?
def initialize(&block)
instance_eval(&block)
end
def answer!
puts "Howdy?"
end
Phone.new { answer! }

57. The Metaprogramming
.instance_eval
.class_eval
.define_method
.send
.method_missing
.instance_variable_set / get

59. Ruby
Interpreted
Dynamic
Object-oriented
General purpose

60. Ruby
Interpreted
Dynamic
Object-oriented
General purpose FUN

61. And profit!

62. Time for fun!
house = House.new(2, 4, 5)
house.floors # 2
house.volume
# Volume is 120 cubic
meters.
house.needs_elevator? # Yes

63. Time for fun! And magic
describe "WiFi" do
ssid "ruby"
password "vilnius"
end
# { "WiFi": { "ssid": "ruby",
"password": "vilnius" } }

64. “Answers”
bit.ly/vilniusrb-1
bit.ly/vilniusrb-2

65. Open source & gems
gem install credit_card_validator
require "credit_card_validator"
number = '1111 2222 3333 4444'
CreditCardValidator::Validator
.valid?(number) # false

66. Ruby
A programmer’s best friend

67. Vilniaus Ruby bendruomenė
Questions.any?