The document discusses dynamic languages, highlighting their characteristics such as dynamic typing and flexible object models, which result in shorter and more reusable code. It contrasts dynamic languages with static languages, emphasizing that in dynamic languages, the programmer has greater control over the programming process. Examples of dynamic languages mentioned include Ruby, Python, JavaScript, and Lisp.

1. Dynamic languages
Reuven M. Lerner • reuven@lerner.co.il
Software Craftsmanship Group, Tel Aviv
March 22nd, 2011
1

2. Who am I?
• Web developer, software architect,
consultant, trainer
• Linux Journal columnist since 1996
• Mostly Ruby on Rails + PostgreSQL, but
also Python, PHP, jQuery, and lots more...
2

3. Language wars!
• Static vs. dynamic languages
• I’m here representing the good guys
• (Just kidding. Mostly.)
• Not just a different language — a different
mindset and set of expectations
3

4. What is a dynamic
language?
• Dynamic typing
• Usually interpreted (or JIT compiled)
• Interactive shell for experimenting
• Closures (anonymous code blocks)
• Flexible, “living” object model
• Result: Short, powerful, reusable code
4

5. Who is in charge?
• Static language: The language is in charge,
and it’s for your own good!
• Dynamic language: The programmer is in
charge, and changes the language to suit his
or her needs
5

6. 6

7. Examples
• Lisp
• Smalltalk
• Python
• Ruby
• JavaScript
7

8. Examples
• Lisp
• Smalltalk
• Python
• Ruby
• JavaScript
7

9. Values, not variables,
have types
x = 5
=> 5
x.class
=> Fixnum
x = [1,2,3]
=> [1, 2, 3]
x.class
=> Array
8

10. Values, not variables,
have types
x = 5
=> 5
x.class
=> Fixnum
x = [1,2,3]
=> [1, 2, 3]
x.class
=> Array
8

11. Values, not variables,
have types
x = 5
=> 5
x.class
=> Fixnum
x = [1,2,3]
=> [1, 2, 3]
x.class
=> Array
8

12. Values, not variables,
have types
x = 5
=> 5
x.class
=> Fixnum
x = [1,2,3]
=> [1, 2, 3]
x.class
=> Array
8

13. Values, not variables,
have types
x = 5
=> 5
x.class
=> Fixnum
x = [1,2,3]
=> [1, 2, 3]
x.class
=> Array
8

14. Less code!
• No need for variable declarations
• No function parameter declarations
• No function return-type declarations
9

15. Ahhhh!
• Are you serious?
• Can real software be developed without a
compiler and type checking?
• How can you possibly work this way?
10

16. Ahhhh!
• Are you serious?
• Can real software be developed without a
compiler and type checking?
• How can you possibly work this way?
• Answer:Very well, thank you.
10

17. 11

18. Flexible collections
a = [1, 2, 'three', [4, 5, 6]]
=> [1, 2, "three", [4, 5, 6]]
a.length
=> 4
a << {first_name:'Reuven',
last_name:'Lerner'}
=> [1, 2, "three", [4, 5, 6],
{:first_name=>"Reuven",
:last_name=>"Lerner"}]
12

19. Flexible collections
Integer
a = [1, 2, 'three', [4, 5, 6]]
=> [1, 2, "three", [4, 5, 6]]
a.length
=> 4
a << {first_name:'Reuven',
last_name:'Lerner'}
=> [1, 2, "three", [4, 5, 6],
{:first_name=>"Reuven",
:last_name=>"Lerner"}]
12

20. Flexible collections
Integer String
a = [1, 2, 'three', [4, 5, 6]]
=> [1, 2, "three", [4, 5, 6]]
a.length
=> 4
a << {first_name:'Reuven',
last_name:'Lerner'}
=> [1, 2, "three", [4, 5, 6],
{:first_name=>"Reuven",
:last_name=>"Lerner"}]
12

21. Flexible collections
Integer String Array
a = [1, 2, 'three', [4, 5, 6]]
=> [1, 2, "three", [4, 5, 6]]
a.length
=> 4
a << {first_name:'Reuven',
last_name:'Lerner'}
=> [1, 2, "three", [4, 5, 6],
{:first_name=>"Reuven",
:last_name=>"Lerner"}]
12

22. Flexible collections
Integer String Array
a = [1, 2, 'three', [4, 5, 6]]
=> [1, 2, "three", [4, 5, 6]]
a.length
=> 4
a << {first_name:'Reuven',
last_name:'Lerner'} Hash
=> [1, 2, "three", [4, 5, 6],
{:first_name=>"Reuven",
:last_name=>"Lerner"}]
12

23. Collections
• Built-in collections (arrays, hashes) are good
for most basic data structures
• Only create a class when you need to!
• Learning to use arrays and hashes is a key
part of dynamic programming, and can save
you lots of time
13

24. Functional tricks
• collect (map)
• detect (find)
• select (find_all)
• reject
• inject
14

25. Sorted username list
File.readlines('/etc/passwd').
reject {|line| line =~ /^#/}.
map {|line| line.split(':').
first}.
sort
15

26. Sorted username list
File.readlines('/etc/passwd').
reject {|line| line =~ /^#/}.
map {|line| line.split(':').
first}.
sort
15

27. Sorted username list
File.readlines('/etc/passwd').
reject {|line| line =~ /^#/}.
map {|line| line.split(':').
first}.
sort
15

28. Sorted username list
File.readlines('/etc/passwd').
reject {|line| line =~ /^#/}.
map {|line| line.split(':').
first}.
sort
15

29. Sorted username list
File.readlines('/etc/passwd').
reject {|line| line =~ /^#/}.
map {|line| line.split(':').
first}.
sort
15

30. Sorted username list
File.readlines('/etc/passwd').
reject {|line| line =~ /^#/}.
map {|line| line.split(':').
first}.
sort
15

31. Domain counter
domains = Hash.new(0)
File.readlines(list_member_file).each do |line|
email, domain = line.chomp.split('@')
domains[domain.downcase] += 1
end
domains.sort_by {|d| -d[1] }.
each {|d| puts "#{d[1]} #{d[0]}" }
domains.sort_by {|d| [-d[1], d[0]] }.
each {|d| puts "#{d[1]} #{d[0]}" }
16

32. Domain counter
domains = Hash.new(0)
File.readlines(list_member_file).each do |line|
email, domain = line.chomp.split('@')
domains[domain.downcase] += 1
end
domains.sort_by {|d| -d[1] }.
each {|d| puts "#{d[1]} #{d[0]}" }
domains.sort_by {|d| [-d[1], d[0]] }.
each {|d| puts "#{d[1]} #{d[0]}" }
16

33. Domain counter
domains = Hash.new(0)
File.readlines(list_member_file).each do |line|
email, domain = line.chomp.split('@')
domains[domain.downcase] += 1
end
domains.sort_by {|d| -d[1] }.
each {|d| puts "#{d[1]} #{d[0]}" }
domains.sort_by {|d| [-d[1], d[0]] }.
each {|d| puts "#{d[1]} #{d[0]}" }
16

34. Domain counter
domains = Hash.new(0)
File.readlines(list_member_file).each do |line|
email, domain = line.chomp.split('@')
domains[domain.downcase] += 1
end
domains.sort_by {|d| -d[1] }.
each {|d| puts "#{d[1]} #{d[0]}" }
domains.sort_by {|d| [-d[1], d[0]] }.
each {|d| puts "#{d[1]} #{d[0]}" }
16

35. Domain counter
domains = Hash.new(0)
File.readlines(list_member_file).each do |line|
email, domain = line.chomp.split('@')
domains[domain.downcase] += 1
end
domains.sort_by {|d| -d[1] }.
each {|d| puts "#{d[1]} #{d[0]}" }
domains.sort_by {|d| [-d[1], d[0]] }.
each {|d| puts "#{d[1]} #{d[0]}" }
16

36. Domain counter
domains = Hash.new(0)
File.readlines(list_member_file).each do |line|
email, domain = line.chomp.split('@')
domains[domain.downcase] += 1
end
domains.sort_by {|d| -d[1] }.
each {|d| puts "#{d[1]} #{d[0]}" }
domains.sort_by {|d| [-d[1], d[0]] }.
each {|d| puts "#{d[1]} #{d[0]}" }
16

37. Domain counter
domains = Hash.new(0)
File.readlines(list_member_file).each do |line|
email, domain = line.chomp.split('@')
domains[domain.downcase] += 1
end
domains.sort_by {|d| -d[1] }.
each {|d| puts "#{d[1]} #{d[0]}" }
domains.sort_by {|d| [-d[1], d[0]] }.
each {|d| puts "#{d[1]} #{d[0]}" }
16

38. Total cost of order
• Total price of an order of books:
total_price = books.
inject(0) do |sum, b|
sum + (b.price * b.quantity)
end
17

39. Real-time require
require 'jobs/a'
require 'jobs/b'
require 'jobs/c'
Dir["#{Rails.root}/app/jobs/
*.rb"].
each { |file| require file }
18

40. Real-time require
require 'jobs/a'
require 'jobs/b'
require 'jobs/c'
Dir["#{Rails.root}/app/jobs/
*.rb"].
each { |file| require file }
18

41. Real-time require
require 'jobs/a'
require 'jobs/b'
require 'jobs/c'
Dir["#{Rails.root}/app/jobs/
*.rb"].
each { |file| require file }
18

42. Classes
• Classes allow you to abstract behavior
• Classes contain data and methods
• It’s easy and fast to create a class
19

43. Defining classes
class Person
end
=> nil
p = Person.new
=> #<Person:0x00000102105740>
p.class
=> Person
p.class.ancestors
=> [Person, Object, Wirble::Shortcuts,
PP::ObjectMixin, Kernel, BasicObject]
20

44. Defining classes
class Person
end
=> nil
p = Person.new
=> #<Person:0x00000102105740>
p.class
=> Person
p.class.ancestors
=> [Person, Object, Wirble::Shortcuts,
PP::ObjectMixin, Kernel, BasicObject]
20

45. Defining classes
class Person
end
=> nil
p = Person.new
=> #<Person:0x00000102105740>
p.class
=> Person
p.class.ancestors
=> [Person, Object, Wirble::Shortcuts,
PP::ObjectMixin, Kernel, BasicObject]
20

46. Defining classes
class Person
end
=> nil
p = Person.new
=> #<Person:0x00000102105740>
p.class
=> Person
p.class.ancestors
=> [Person, Object, Wirble::Shortcuts,
PP::ObjectMixin, Kernel, BasicObject]
20

47. Defining classes
class Person
end
=> nil
p = Person.new
=> #<Person:0x00000102105740>
p.class
=> Person
p.class.ancestors
=> [Person, Object, Wirble::Shortcuts,
PP::ObjectMixin, Kernel, BasicObject]
20

48. Reflection
> p.methods # or Person.instance_methods
=>
[:po, :poc, :pretty_print, :pretty_print_cycle,
:pretty_print_instance_variables, :pretty_print_inspect,
:nil?, :, :, :!, :eql?, :hash, :=>, :class, :singleton_class,
:clone, :dup, :initialize_dup, :initialize_clone, :taint,
:tainted?, :untaint, :untrust, :untrusted?, :trust, :freeze,
:frozen?, :to_s, :inspect, :methods, :singleton_methods,
:protected_methods, :private_methods, :public_methods,
:instance_variables, :instance_variable_get,
:instance_variable_set, :instance_variable_defined?,
:instance_of?, :kind_of?, :is_a?, :tap, :send, :public_send,
:respond_to?, :respond_to_missing?, :extend, :display,
:method, :public_method, :define_singleton_method, :__id__,
:object_id, :to_enum, :enum_for, :pretty_inspect, :ri, :,
:equal?, :!, :!, :instance_eval, :instance_exec, :__send__]
21

49. Predicates
p.methods.grep(/?$/)
=>
[:nil?, :eql?, :tainted?,
:untrusted?, :frozen?,
:instance_variable_defined?,
:instance_of?, :kind_of?, :is_a?,
:respond_to?, :respond_to_missing?,
:equal?]
22

50. “Local” methods
class Person
def blah
"blah"
end
end
=> nil
p = Person.new
p.class.instance_methods -
p.class.superclass.instance_methods
=> [:blah]
23

51. “Local” methods
class Person
def blah
"blah"
end
end
=> nil
p = Person.new
p.class.instance_methods -
p.class.superclass.instance_methods
=> [:blah]
23

52. “Local” methods
class Person
def blah
"blah"
end
end
=> nil
p = Person.new
p.class.instance_methods -
p.class.superclass.instance_methods
=> [:blah]
23

53. “Local” methods
class Person
def blah
"blah"
end
end
=> nil
p = Person.new
p.class.instance_methods -
p.class.superclass.instance_methods
=> [:blah]
23

54. Calling methods
a.length
=> 5
a.send(:length)
=> 5
a.send("length".to_sym)
=> 5
24

55. Calling methods
a.length
=> 5
a.send(:length)
=> 5
a.send("length".to_sym)
=> 5
24

56. Calling methods
a.length
=> 5
a.send(:length)
=> 5
a.send("length".to_sym)
=> 5
24

57. Calling methods
a.length
=> 5
a.send(:length)
=> 5
a.send("length".to_sym)
=> 5
24

58. Preferences become
method calls
def bid_or_ask
is_ask? ? :ask : :bid
end
trade_amount = net_basis *
(end_rate.send(bid_or_ask) -
start_rate.send(bid_or_ask))
25

59. Preferences become
method calls
def bid_or_ask
is_ask? ? :ask : :bid
end
trade_amount = net_basis *
(end_rate.send(bid_or_ask) -
start_rate.send(bid_or_ask))
25

60. Preferences become
method calls
def bid_or_ask
is_ask? ? :ask : :bid
end
trade_amount = net_basis *
(end_rate.send(bid_or_ask) -
start_rate.send(bid_or_ask))
25

61. Define similar methods
['preview', 'applet', 'info',
'procedures', 'discuss', 'files',
'history', 'tags', 'family', 'upload',
'permissions'].each do |tab_name|
define_method(
"browse_#{tab_name}_tab".to_sym ) do
render :layout => 'browse_tab'
end
end
26

62. Define similar methods
['preview', 'applet', 'info',
'procedures', 'discuss', 'files',
'history', 'tags', 'family', 'upload',
'permissions'].each do |tab_name|
define_method(
"browse_#{tab_name}_tab".to_sym ) do
render :layout => 'browse_tab'
end
end
26

63. Define similar methods
['preview', 'applet', 'info',
'procedures', 'discuss', 'files',
'history', 'tags', 'family', 'upload',
'permissions'].each do |tab_name|
define_method(
"browse_#{tab_name}_tab".to_sym ) do
render :layout => 'browse_tab'
end
end
26

64. Define similar methods
['preview', 'applet', 'info',
'procedures', 'discuss', 'files',
'history', 'tags', 'family', 'upload',
'permissions'].each do |tab_name|
define_method(
"browse_#{tab_name}_tab".to_sym ) do
render :layout => 'browse_tab'
end
end
26

65. Define similar methods
['preview', 'applet', 'info',
'procedures', 'discuss', 'files',
'history', 'tags', 'family', 'upload',
'permissions'].each do |tab_name|
define_method(
"browse_#{tab_name}_tab".to_sym ) do
render :layout => 'browse_tab'
end
end
26

66. Searching by result
'a'.what?('A')
"a".upcase == "A"
"a".capitalize == "A"
"a".swapcase == "A"
"a".upcase! == "A"
"a".capitalize! == "A"
"a".swapcase! == "A"
[:upcase, :capitalize, :swapcase,
:upcase!, :capitalize!, :swapcase!]
27

67. Searching by result
'a'.what?('A')
"a".upcase == "A"
"a".capitalize == "A"
"a".swapcase == "A"
"a".upcase! == "A"
"a".capitalize! == "A"
"a".swapcase! == "A"
[:upcase, :capitalize, :swapcase,
:upcase!, :capitalize!, :swapcase!]
27

68. Searching by result
'a'.what?('A')
"a".upcase == "A"
"a".capitalize == "A"
"a".swapcase == "A"
"a".upcase! == "A"
"a".capitalize! == "A"
"a".swapcase! == "A"
[:upcase, :capitalize, :swapcase,
:upcase!, :capitalize!, :swapcase!]
27

69. Searching by result
'a'.what?('A')
"a".upcase == "A"
"a".capitalize == "A"
"a".swapcase == "A"
"a".upcase! == "A"
"a".capitalize! == "A"
"a".swapcase! == "A"
[:upcase, :capitalize, :swapcase,
:upcase!, :capitalize!, :swapcase!]
27

70. Monkey patching!
class Fixnum
def *(other)
self + other
end
end
6*5
=> 11
28

71. Monkey patching!
class Fixnum
def *(other)
self + other
end
end
6*5
=> 11
28

72. Monkey patching!
class Fixnum
def *(other)
self + other
end
end
6*5
=> 11
28

73. Example: “Whiny nils”
• Try to invoke “id” on nil, and Rails will
complain
@y.id
RuntimeError: Called id for nil,
which would mistakenly be 4 -- if
you really wanted the id of nil,
use object_id
29

74. Example: RSpec
it "should have a unique name" do
c1 = Currency.new(@valid_attributes)
c1.save!
c2 =
Currency.new(
:name => @valid_attributes[:name],
:abbreviation => 'XYZ')
c1.should be_valid
c2.should_not be_valid
end
30

75. Example: RSpec
it "should have a unique name" do
c1 = Currency.new(@valid_attributes)
c1.save!
c2 =
Currency.new(
:name => @valid_attributes[:name],
:abbreviation => 'XYZ')
c1.should be_valid
c2.should_not be_valid
end
30

76. Example: RSpec
it "should have a unique name" do
c1 = Currency.new(@valid_attributes)
c1.save!
c2 =
Currency.new(
:name => @valid_attributes[:name],
:abbreviation => 'XYZ')
c1.should be_valid
c2.should_not be_valid
end
30

77. method_missing
• If no method exists, then method_missing
is invoked, passing the method name, args
31

78. Dynamic finders
Reading.find_all_by_longitude_and_d
evice_id(0, 3)
=> [#<Reading id: 46, longitude:
#<BigDecimal:24439a8,'0.0',9(18)>,
latitude: ... ]
Reading.instance_methods.grep(/
long/)
=> []
32

79. Dynamic finders
Reading.find_all_by_longitude_and_d
evice_id(0, 3)
=> [#<Reading id: 46, longitude:
#<BigDecimal:24439a8,'0.0',9(18)>,
latitude: ... ]
Reading.instance_methods.grep(/
long/)
=> []
32

80. Dynamic finders
Reading.find_all_by_longitude_and_d
evice_id(0, 3)
=> [#<Reading id: 46, longitude:
#<BigDecimal:24439a8,'0.0',9(18)>,
latitude: ... ]
Reading.instance_methods.grep(/
long/)
=> []
32

81. Hash methods as keys
class Hash
def method_missing(name, *args)
if has_key?(name)
self[name]
end
end
end
33

82. Example
h = {a:1, b:2} => 3
=> {:a=>1, :b=>2} h.c
h[:a] => nil
=> 1 h[:d] = 4
h.a => 4
=> 1 h.d
h['c'] = 3 => 4
34

83. Example
h = {a:1, b:2} => 3
=> {:a=>1, :b=>2} h.c
h[:a] => nil
=> 1 h[:d] = 4
h.a => 4
=> 1 h.d
h['c'] = 3 => 4
34

84. Example
h = {a:1, b:2} => 3
=> {:a=>1, :b=>2} h.c
h[:a] => nil
=> 1 h[:d] = 4
h.a => 4
=> 1 h.d
h['c'] = 3 => 4
34

85. Example
h = {a:1, b:2} => 3
=> {:a=>1, :b=>2} h.c
h[:a] => nil
=> 1 h[:d] = 4
h.a => 4
=> 1 h.d
h['c'] = 3 => 4
34

86. Example
h = {a:1, b:2} => 3
=> {:a=>1, :b=>2} h.c
h[:a] => nil
=> 1 h[:d] = 4
h.a => 4
=> 1 h.d
h['c'] = 3 => 4
34

87. Example
h = {a:1, b:2} => 3
=> {:a=>1, :b=>2} h.c
h[:a] => nil
=> 1 h[:d] = 4
h.a => 4
=> 1 h.d
h['c'] = 3 => 4
34

88. Example
h = {a:1, b:2} => 3
=> {:a=>1, :b=>2} h.c
h[:a] => nil
=> 1 h[:d] = 4
h.a => 4
=> 1 h.d
h['c'] = 3 => 4
34

89. Example
h = {a:1, b:2} => 3
=> {:a=>1, :b=>2} h.c
h[:a] => nil
=> 1 h[:d] = 4
h.a => 4
=> 1 h.d
h['c'] = 3 => 4
34

90. Hash method access
class Hash
def method_missing(method_name, *arguments)
if has_key?(method_name)
self[method_name]
elsif has_key?(method_name.to_s)
self[method_name.to_s]
else
nil
end
end
end
35

91. Hash method access
class Hash
def method_missing(method_name, *arguments)
if has_key?(method_name)
self[method_name]
elsif has_key?(method_name.to_s)
self[method_name.to_s]
else
nil
end
end
end
35

92. Hash method access
class Hash
def method_missing(method_name, *arguments)
if has_key?(method_name)
self[method_name]
elsif has_key?(method_name.to_s)
self[method_name.to_s]
else
nil
end
end
end
35

93. Hash method access
class Hash
def method_missing(method_name, *arguments)
if has_key?(method_name)
self[method_name]
elsif has_key?(method_name.to_s)
self[method_name.to_s]
else
nil
end
end
end
35

94. Hash method access
class Hash
def method_missing(method_name, *arguments)
if has_key?(method_name)
self[method_name]
elsif has_key?(method_name.to_s)
self[method_name.to_s]
else
nil
end
end
end
35

95. Hash method access
class Hash
def method_missing(method_name, *arguments)
if has_key?(method_name)
self[method_name]
elsif has_key?(method_name.to_s)
self[method_name.to_s]
else
nil
end
end
end
35

96. xml.instruct! :xml, :version=>"1.0"
xml.rss(:version=>"2.0"){
xml.channel{
xml.title("Modeling Commons updates")
xml.link("http://modelingcommons.org/")
xml.description("NetLogo Modeling Commons")
xml.language('en-us')
for update in @updates
xml.item do
xml.title(post.title)
xml.description(post.html_content)
xml.author("Your Name Here")
xml.pubDate(post.created_on.strftime("%a,
%d %b %Y %H:%M:%S %z"))
xml.link(post.link)
xml.guid(post.link)
end
end
}
}
36

97. xml.instruct! :xml, :version=>"1.0"
xml.rss(:version=>"2.0"){
xml.channel{
xml.title("Modeling Commons updates")
xml.link("http://modelingcommons.org/")
xml.description("NetLogo Modeling Commons")
xml.language('en-us')
for update in @updates
xml.item do
xml.title(post.title)
xml.description(post.html_content)
xml.author("Your Name Here")
xml.pubDate(post.created_on.strftime("%a,
%d %b %Y %H:%M:%S %z"))
xml.link(post.link)
xml.guid(post.link)
end
end
}
}
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98. xml.instruct! :xml, :version=>"1.0"
xml.rss(:version=>"2.0"){
xml.channel{
xml.title("Modeling Commons updates")
xml.link("http://modelingcommons.org/")
xml.description("NetLogo Modeling Commons")
xml.language('en-us')
for update in @updates
xml.item do
xml.title(post.title)
xml.description(post.html_content)
xml.author("Your Name Here")
xml.pubDate(post.created_on.strftime("%a,
%d %b %Y %H:%M:%S %z"))
xml.link(post.link)
xml.guid(post.link)
end
end
}
}
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99. xml.instruct! :xml, :version=>"1.0"
xml.rss(:version=>"2.0"){
xml.channel{
xml.title("Modeling Commons updates")
xml.link("http://modelingcommons.org/")
xml.description("NetLogo Modeling Commons")
xml.language('en-us')
for update in @updates
xml.item do
xml.title(post.title)
xml.description(post.html_content)
xml.author("Your Name Here")
xml.pubDate(post.created_on.strftime("%a,
%d %b %Y %H:%M:%S %z"))
xml.link(post.link)
xml.guid(post.link)
end
end
}
}
36

100. xml.instruct! :xml, :version=>"1.0"
xml.rss(:version=>"2.0"){
xml.channel{
xml.title("Modeling Commons updates")
xml.link("http://modelingcommons.org/")
xml.description("NetLogo Modeling Commons")
xml.language('en-us')
for update in @updates
xml.item do
xml.title(post.title)
xml.description(post.html_content)
xml.author("Your Name Here")
xml.pubDate(post.created_on.strftime("%a,
%d %b %Y %H:%M:%S %z"))
xml.link(post.link)
xml.guid(post.link)
end
end
}
}
36

101. xml.instruct! :xml, :version=>"1.0"
xml.rss(:version=>"2.0"){
xml.channel{
xml.title("Modeling Commons updates")
xml.link("http://modelingcommons.org/")
xml.description("NetLogo Modeling Commons")
xml.language('en-us')
for update in @updates
xml.item do
xml.title(post.title)
xml.description(post.html_content)
xml.author("Your Name Here")
xml.pubDate(post.created_on.strftime("%a,
%d %b %Y %H:%M:%S %z"))
xml.link(post.link)
xml.guid(post.link)
end
end
}
}
36

102. Module includes
module MyStuff
def self.included(klass)
klass.extend(ClassMethods)
end
module ClassMethods
def foo; end
end
end
37

103. Module includes
module MyStuff
def self.included(klass)
klass.extend(ClassMethods)
end
module ClassMethods
def foo; end
end
end
37

104. Module includes
module MyStuff
def self.included(klass)
klass.extend(ClassMethods)
end
module ClassMethods
def foo; end
end
end
37

105. Module includes
module MyStuff
def self.included(klass)
klass.extend(ClassMethods)
end
module ClassMethods
def foo; end
end
end
37

106. Thanks!
(Any questions?)
• Call me: 054-496-8405
• E-mail me: reuven@lerner.co.il
• Interrupt me: reuvenlerner (Skype/AIM)
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