Thinking in Objects RubyConf 2012

This talk presents OOP fundamentals, and a basic vocabulary that helps to think about programming in OOP languages.

Transcript

1. Thinking in Objects
2. @joshsusser CTO - Cognitive Health Innovations RubyRogues GoGaRuCo
4. Perspective is worth 80 I.Q. points. –Alan Kay
6. http://www.flickr.com/photos/xlibber/2962488972
7. Object = Identity + Behavior + State OOP = Objects + Encapsulation + Polymorphism + Inheritance
8. It’s all about MESSAGES
10. Smalltalk (OOP) LISP (FP) Perl (scripting)
11. Object = Identity + Behavior + State
12. Identity $ nslookup github.com 207.97.227.239
13. Identity s = "foo" s.object_id #=> 123450 t = "foo" #=> "foo" t.object_id #=> 123780
14. Identity s = "foo"; t = "foo" s == t #=> true s.equal?(t) #=> false
15. Identity s = "foo"; t = "foo" s << "d" #=> "food" t #=> "foo"
16. Behavior "foo".methods #=> [:<=>, :==, :===, :eql?, :hash, :casecmp, :+, :*, :%, :[], :[]=, :insert, :length, :size, :bytesize, :empty?, :=~, :match, :succ, :succ!, :next, :next!, :upto, :index, :reverse, ...]
17. methods def even? self % 2 == 0 end def odd? !self.even? end
18. Object = Identity + Behavior + State
19. uniques nil true, false :ruby, :rails
20. uniques GUEST = Object.new def GUEST.name "Guest User" end
21. State s = "foo" s << "d" #=> "food" s.length #=> 4
22. State = Behavior
23. Uniform Access attr_accessor :first_name
24. Uniform Access def first_name @first_name end
25. Uniform Access def first_name @full_name.split(" ").first end
26. JavaScript user.firstName user.firstName()
27. GET /index •WEB_ROOT/index.html •app/views/home/index.erb •memcached / varnish
28. Encapsulation
29. Polymorphism Duck-typing Protocol API
30. Object-based Objects + Encapsulation + Polymorphism dynamic binding
31. Inheritance • Implementation • Type
32. Delegation • Composition - Forwardable • Prototypes - JavaScript, SELF
33. Delegation IS Inheritance Lynn Andrea Stein OOPSLA 1987 "Treaty of Orlando"
34. OOP= Objects + Encapsulation + Polymorphism + Inheritance
35. It’s all about MESSAGES
36. call a method
37. • delegation • method_missing call a method
38. send a message call a method
39. class Person def name; @name; end end class Employee < Person def name; "#{@name}, #{@title}"; end end class Letter # address letter to recipient's name without title def recipient_name super_name = Person.instance_method(:name) bound_name = super_name.bind(@recipient) bound_name.call end end
40. class Person def name; @name; end end class Employee < Person def name; "#{@name}, #{@title}"; end end class Letter # address letter to recipient's name without title def recipient_name super_name = Person.instance_method(:name) bound_name = super_name.bind(@recipient) bound_name.call end end
41. use objects •blocks & lambdas •hashes & arrays •symbols (names) instead of
42. use objects reification unites behavior with data
43. validation validates_presence_of :phone validate { |r| r.home_phone? || r.cell_phone? } validate :validate_has_a_phone validates_with HasAPhone
44. polymorphism Method lookup is fast. Testing class type is slow and messy.
45. def scope if @product if current_api_user.has_spree_role?("admin") unless params[:show_deleted] variants = @product.variants_including_master else variants = @product.variants_including_master_and_deleted end else variants = @product.variants_including_master end else variants = Variant.scoped if current_api_user.has_spree_role?("admin") unless params[:show_deleted] variants = Variant.active end end end variants end
46. def scope if @product if current_api_user.has_spree_role?("admin") unless params[:show_deleted] variants = @product.variants_including_master else variants = @product.variants_including_master_and_deleted end else variants = @product.variants_including_master end else variants = Variant.scoped if current_api_user.has_spree_role?("admin") unless params[:show_deleted] variants = Variant.active end end end variants end
47. class Variant class << self alias_method :variants_including_master_and_deleted, :scoped alias_method :variants_including_master, :active end end def scope scoper = @product || Variant if current_api_user.has_spree_role?("admin") && params[:show_deleted] scoper.variants_including_master_and_deleted else scoper.variants_including_master end end
48. Object = Identity + Behavior + State OOP = Objects + Encapsulation + Polymorphism + Inheritance Messages = secret sauce