SFD 2011 Cavite, STI Southwoods

1. Ruby on Rails

2. Ruby
http://ruby-lang.org

3. is...
...a language that focuses on simplicity
puts "hello world"

4. is...
...an open source programming
language
http://www.ruby-lang.org

5. is...
...a language with different
implementations

6. is...
...a dynamic language
X = "Hello world"
puts x #outputs "Hello World"
X = 10
puts x #outputs "10"

7. is...
...an interpreted language
irb(main):001:0> x = "Hello World"
=> "Hello World"
irb(main):002:0> puts x
Hello World
=> nil

8. Running Ruby
via irb (Interactive RuBy):
C:Usersuser> irb
irb(main):001:0> puts "Hello World"
Hello World
=> nil
irb(main):002:0>

9. Running Ruby
via ruby command:
C:Usersuser> ruby hello.rb
Hello World

10. is...
...a language that focuses on simplicity
Look Ma, no IDE!

11. is...
...a language that focuses on simplicity
Ok, there are IDEs

12. is...
...an object oriented language
class Person
def greet
puts "Hello!"
end
end
p = Person.new()
p.hello()

13. is...
...a "true" object oriented language
puts 1.even?() #outputs false
puts nil.methods() #no error!

14. is...
...a language that focuses on simplicity
puts 1.even? #outputs false
puts nil.methods #no error!

15. is...
...a functional language
employees = ["Alex", "Bob", "Eve"]
employees.each do |employee|
puts "Hello #{employee}"
end

16. is...
...a functional language
emps = ["Alex", "Bob", "Eve"]
reverse = emps.map { |e| e.reverse }

17. is...
...a functional language
employees = ["Alex", "Bob", "Eve"]
emps = employees.sort do |x, y|
x.reverse <=> y.reverse
end

18. is...
...a functional language
hello = Proc.new do |string|
puts "Hello #{string}"
end
hello.call "Alice"
hello.call "Bob"

19. is...
...a flexible language
class Numeric
def plus(x)
self.+(x)
end
end
y = 5.plus 6

20. Ruby Basics

21. Comments
# pound/hash/sharp/octothorpe
# for single line comments
==begin
for multiline comments
* very rare
==end

22. Variables
snake_case = 1 # local variable
CamelCase = 200 # constant

23. Numbers
a_number = 1
with_delimeter = 1_000_000
decimal = 100.01

24. Auto-convert on Overflow
large = 1073741823
puts large.class #outputs Fixnum
large = large + 1
puts large.class #outputs Bignum

25. Strings
single_quote = 'this string'
double_quote = "double 'quote'"
escape = "double "quote""

26. String Interpolation
puts "20 * 20 = #{20 * 20}"

27. Symbols
:this_is_a_symbol
#symbols are like constants
puts "test".object_id
puts "test".object_id #different
puts :test.object_id
puts :test.object_id #same

28. Operators
# Everything works as you expect
# +, -, *, /, %, &&, ||, ==, etc
# no ++ or --, but there's **
# and you could use "and" in
# place of &&, or "or" <-> ||

29. if - else
# no parenthesis needed
if x < 0
puts "x is negative"
elsif x > 0
puts "x is positive"
else
puts "x is zero"
end

30. if, single line
puts "x is negative" if x < 0

31. unless
unless people_count > capacity
puts "There are available seats"
end

32. Arrays
list = [1, "two", 3]
list << "another item"
list[0] = "uno"
puts list[1]

33. Hashes
prices = {:soda => 30, :chips => 5}
puts prices[:soda]
prices[:rice] = 12.50

34. Iteration and Blocks
list.each { |x| puts x }
list.each do |x|
puts x
end

35. More Iteration and Blocks
prices.each_pair do |key, value|
puts "#{key}: #{value}"
end

36. More Iteration
100.times { puts "Hello" }
100.times { |x| puts "Hello #{x}" }
100.downto(50) { |y| puts y }

37. Ranges
(1..100).each { |w| puts w }
# .. is inclusive
puts (200..300).to_a
# .. is right side exclusive
puts (200...300).to_a

38. Methods
def greet(name)
puts "Hello #{name}"
end
greet "Juan"

39. Methods, default argument
def greet(name = "there")
puts "Hello #{name}"
end
greet

40. Methods, variable scope
x, y = 2, 1
def cube(x)
y = x**3
return y
end
puts cube(x)
puts y

41. methods, return value
def cube(x)
y = x**3 #last line is returned
end

42. OOP: Classes
class Person
end
p = Person.new

43. OOP: instance methods
class Person
def greet
puts "Hello"
end
end
p = Person.new
p.greet

44. OOP: constructors
class Person
def initialize
puts "Hello"
end
end
p = Person.new

45. OOP: instance variables
class Person
def initialize(name)
@name = name #var starts with @
end
end
p = Person.new(name)

46. OOP: class methods
class Person
def self.species
"Homo Sapiens"
end
end
puts Person.species

47. OOP: class variables
class Person
def initialize
@@instantiated = true
end
end

48. OOP: getters/setters
class Person
def name=(name)
@name = name #var starts with @
end
def name
name
end
end
p = Person.new(name)
p.name = "Joe"

49. OOP: getters/setters
class Person
attr_accessor :name
end
p = Person.new
p.name = "Joe"
puts p.name

50. OOP: inheritance
class Student < Person
attr_accessor :school
end
s = Student.new
s.school = "XYZ High"
s.name = "Joe"

51. Modules
#can't be instantiated or subclassed
module Swimmer
def swim
puts "I'm swimming!"
end
end

52. Modules as Mixin
module Swimmer
def swim
puts "I'm swimming!"
end
end
class Person
include Swimmer
end
Person.new.swim #outputs "I'm swimming!"

53. Modules for Namespacing
module X
class D
end
end
module Y
class D
end
end
X::D.new #different class from Y::D

54. Modules for Namespacing
# modules and classes are constants!
module MyConstants
MeaningOfLife = 42
end
puts MyConstants::MeaningOfLife

55. Ruby libraries are packaged
and distributed as
RubyGems

59. Ruby on Rails
is a web framework built
in Ruby

60. pauliwoll

61. globevisions

62. Installing
For this seminar, we will use the
Rails 3.0 installer from
RailsInstaller.org
(Rails Installer v1.3.0)

63. Why Rails 3.0 instead of 3.1?

65. Testing Rails
C:Usersuser> cd Sitessample
C:Sitessample> rails server

66. Testing Rails
You should be able to access the server
at http://localhost:3000

67. Testing Rails
All static files in the /public directory
will now be accessible in
http://localhost:3000

68. Building your App
(Press Ctrl-C to terminate the server)
C:Sitessample> cd ..
C:Sites> rails new [app_name]
C:Sites> cd app_name

69. Model View Controller

70. 1
Controller
4 3 2
View Model DB

71. cactusbones

72. Creating a Controller and a View
$ rails generate controller pages demo

73. Creating a Controller and a View
Start the server via rails server
View the page at
http://localhost:3000/pages/demo

74. The View
Open the erb (Embedded RuBy) file
app/views/pages/demo.html.erb
<h1>Pages#demo</h1>
<p>Find me in app/views/pages/demo.html.erb</p>

75. Expressions
Ruby expressions inside <%= %> are evaluated
and inserted into the HTML
<p>2¹⁰ = <%= 2**10 %></p>

76. Scriptlets
Ruby code inside <% %> are executed as-is
<ul>
<% 100.times do |x| %>
<li><%= x %></li>
<% end %>
</ul>

77. The Controller
app/controllers/pages_controller.rb
class PagesController < ApplicationController
def demo
end
end

78. Instance Variables
instance variables in the controller are
copied when rendering the view
#app/controllers/pages_controller.rb
class PagesController < ApplicationController
def demo
@message = "Hello World"
end
end
#app/views/pages/demo.html.erb
<p><%= @message %></p>

79. Parameters
HTTP request parameter data are
accessible via the params hash
#app/controllers/pages_controller.rb
class PagesController < ApplicationController
def demo
@message = "Hello #{ params[:name] }"
end
end
# http://localhost:3000/pages/demo?name=John

80. Controller Routing
incoming requests go through
config/routes.rb
to determine which controller/action should
handle it
YourApp::Application.routes.draw do
get "pages/demo" #all requests to /pages/demo
#are handled by the "demo"
#action at the PagesController
...

81. Controller Routing
YourApp::Application.routes.draw do
# replace get "pages/demo" with this line to
# capture http://localhost:3000/demo instead
match "demo" => "pages#demo"
...

82. Controller Routing
YourApp::Application.routes.draw do
# delete public/index.html
# and replace the previous example with this to
# capture http://localhost:3000/
root :to => "pages#demo"
...

83. Creating a Model
Open a new command prompt (no need to stop
the server), go to your application's directory
and run the following rails generate command:
$ rails generate model visit

84. Modifying the Database
$ rake db:migrate
This will execute the "migration" files generated
along with the model that define the
DB change to be applied

85. Model code inside Controller
#app/controllers/pages_controller.rb
class PagesController < ApplicationController
def demo
Visit.create
@visit_count = Visit.count
@last_visit = Visit.last.created_at
end
end
#app/views/pages/demo.html.erb
<p>Visits logged in DB: <%= @visit_count %></p>
<p>Last Visit: <%= @last_visit %></p>

86. Cheating with Scaffold
(kasi inaantok na kayo)

87. Blog in 2 commands
$ rails g scaffold blog_entry
title:string entry:text
$ rake db:migrate
Now go to
http://localhost:3000/blog_entries

88. Something More Complicated
$ rails g scaffold delivery
item:string quantity:integer
price:decimal paid:boolean
address:text deliver_by:datetime
$ rake db:migrate
Now go to
http://localhost:3000/deliveries

89. Convention over
Configuration

90. Don't Repeat Yourself
(DRY)

91. Representational State
Transfer
(REST)

92. … and that's it.
Please refer to the handouts
if you want more info about Ruby or
Ruby on Rails

93. Thank you for listening!
Questions?
Philippine Ruby Users Group:
pinoyrb.org
me: bryanbibat.net | @bry_bibat

94. The seminar should be
finished at this point but we
still have time...
...**** it, Let's do it LIVE!