Ruby Crush

A Metaprogramming Primer

Transcript

1. Ruby Crush A Metaprograming Primer Wednesday, March 7, 2012
2. Predicates This primer is intended to introduce metaprogramming concepts. Wednesday, March 7, 2012
3. Definition Wednesday, March 7, 2012
4. Definition Code that writes code Wednesday, March 7, 2012
5. Definition Code that writes code Like erb? Wednesday, March 7, 2012
6. ERB Wednesday, March 7, 2012
7. ERB HTML Wednesday, March 7, 2012
8. ERB HTML UI Wednesday, March 7, 2012
9. Definition Code that writes code Like erb? Code that modifies code at runtime Wednesday, March 7, 2012
10. Quick Examples Decide which method to call at runtime Wednesday, March 7, 2012
11. Quick Examples Dynamic Dispatch ( Task.send param) Decide which method to call at runtime Wednesday, March 7, 2012
12. Dynamic Dispatch Wednesday, March 7, 2012
13. Dynamic Dispatch Wednesday, March 7, 2012
14. Dynamic Dispatch Wednesday, March 7, 2012
15. Quick Examples Decide how to respond to a method call at runtime Wednesday, March 7, 2012
16. Quick Examples Ghost Methods (Profile.deligates User) Decide how to respond to a method call at runtime Wednesday, March 7, 2012
17. Ghost Methods Wednesday, March 7, 2012
18. Ghost Methods Wednesday, March 7, 2012
19. Ghost Methods Wednesday, March 7, 2012
20. Object Model Because, Metaprogramming is code that modifies code at runtime We need to know about the Ruby Object Model before we go too far. Wednesday, March 7, 2012
21. Object Model Wednesday, March 7, 2012
22. Object Model Whataburger Wednesday, March 7, 2012
23. Object Model Wednesday, March 7, 2012
24. Object Model http:/ /www.atalon.cz/ rb-om/ruby-object- model/ http:/ / www.youtube.com/ watch?v=UyAoUX6GYI8 Wednesday, March 7, 2012
25. Object Model Whataburger Data Structure in Detail http:/ /www.atalon.cz/ rb-om/ruby-object- model/ http:/ / www.youtube.com/ watch?v=UyAoUX6GYI8 Wednesday, March 7, 2012
26. Object Model Whataburger Data Structure in Detail Movie http:/ /www.atalon.cz/ rb-om/ruby-object- model/ http:/ / www.youtube.com/ watch?v=UyAoUX6GYI8 Wednesday, March 7, 2012
27. Object Model Whataburger Data Structure in Detail Movie My take on it http:/ /www.atalon.cz/ rb-om/ruby-object- model/ http:/ / www.youtube.com/ watch?v=UyAoUX6GYI8 Wednesday, March 7, 2012
28. Object Model Wednesday, March 7, 2012
29. Object Model Wednesday, March 7, 2012
30. Object Model Wednesday, March 7, 2012
31. Object Model Wednesday, March 7, 2012
32. Object Model Wednesday, March 7, 2012
33. Object Model Wednesday, March 7, 2012
34. Object Model Wednesday, March 7, 2012
35. Object Model Super Wednesday, March 7, 2012
36. Object Model Super Instance Call Chain Wednesday, March 7, 2012
37. Object Model Super Instance Call Chain Class Call Chain Wednesday, March 7, 2012
38. Object Model (Instance Chain) Instance Call Chain Wednesday, March 7, 2012
39. Object Model (Class Chain) Class Call Chain Wednesday, March 7, 2012
40. Object Model (Overlap Chain) Class Call Chain Instance Call Chain Wednesday, March 7, 2012
41. Object Model (Overlap Chain) Class Call Chain Instance Call Chain Wednesday, March 7, 2012
42. Object Model Wednesday, March 7, 2012
43. Object Model Wednesday, March 7, 2012
44. Object Model Wednesday, March 7, 2012
45. Object Model Instance Call Chain Wednesday, March 7, 2012
46. Object Model Class Call Chain Instance Call Chain Wednesday, March 7, 2012
47. Object Model Include Class Call Chain Instance Call Chain Wednesday, March 7, 2012
48. Object Model Include Extend Class Call Chain Instance Call Chain Wednesday, March 7, 2012
49. More Examples Wednesday, March 7, 2012
50. More Examples Class Macros: attr_accessor Wednesday, March 7, 2012
51. Class Macros Wednesday, March 7, 2012
52. Class Macros Wednesday, March 7, 2012
53. Class Macros Wednesday, March 7, 2012
54. Class Macros Wednesday, March 7, 2012
55. Class Macros Wednesday, March 7, 2012
56. Class Macros Wednesday, March 7, 2012
57. More Examples Make something practical Wednesday, March 7, 2012
58. More Examples Class Macros: inherits_from Make something practical Wednesday, March 7, 2012
59. pseudo_inheritance Problem: How do we overcome different paradigms between OO and RDBMS to allow ActiveRecord (AR) objects to inherit from AR objects? Both systems have objects with Behavior, Identity & State. OO objects that inherit from each other should have direct access to all superclasses’ behavior identity and state. RDBMS entities relate to each other. RDBMS entries should normalize state across multiple tables. Because AR stores state in RDBMS, objects that should inherit from other AR objects are required to use composition. Can we use the tools presented in this talk to overcome these limitations? Wednesday, March 7, 2012
60. pseudo_inheritance Example: Our system has users, profiles, hosts, presenters and topics. A user is anyone with access to the system, each user has a profile that describes the user, hosts are users who host a topic, presenters are users who present a topic and topics are well, topics. Users can host and present multiple topics. Wednesday, March 7, 2012
61. pseudo_inheritance Objects class User < ARB has_one :profile class Profile < ARB belongs_to :user has_many :hosts has_many :presenters class Host < ARB belongs_to :profile class Presenter < ARB belongs_to :profile class Topic < ARB has_one :host has_one :presenter Tables users ------------------- profiles profiles ------------< hosts profiles ------------< presenters topics ---------------< hosts ---------------< presenters So we have: To get a Topic’s presenter’s email: @topic.presenter.profile.user.email Wednesday, March 7, 2012
62. pseudo_inheritance Objects class User < ARB class Profile < User class Host < Profile class Presenter < Profile class Topic < ARB has_one :host has_one :presenter Tables users ------------------- profiles profiles ------------< hosts profiles ------------< presenters topics ---------------< hosts ---------------< presenters We should have: To get a Topic’s presenter’s email: @topic.presenter.email Wednesday, March 7, 2012
63. pseudo_inheritance Wednesday, March 7, 2012
64. pseudo_inheritance ARB Wednesday, March 7, 2012
65. pseudo_inheritance ARB Pseudo Inheritance Wednesday, March 7, 2012
66. pseudo_inheritance Wednesday, March 7, 2012
67. pseudo_inheritance Wednesday, March 7, 2012
68. pseudo_inheritance Wednesday, March 7, 2012
69. pseudo_inheritance Wednesday, March 7, 2012
70. pseudo_inheritance class Presenter < ARB class Host < ARB Implementation Wednesday, March 7, 2012
71. Don’t Forget to Remember Yukirhiro Matsumoto: ... computers don't mind if I must make effort to communicate with them or if it is easy to communicate with them... . We humans care about the effort we pay. Often people, especially computer engineers, focus on the machines. They think, "By doing this, the machine will run faster. By doing this, the machine will run more effectively. By doing this, the machine will something something something." They are focusing on machines. But in fact we need to focus on humans, on how humans care about doing programming or operating the application of the machines. Wednesday, March 7, 2012
72. Bibliography Venners, Bill. The Philosophy of Ruby: A conversation with Yukihiro Matsumoto, Part I. [Article] (September 29, 2003). Artima Developer, From http://www.artimadeveloper.com/intv/ruby4.html Thomas, Dave, Andy Hunt and Chad Fowler. Programming Ruby 1.9: The Pragmatic Programmers’ Guide. Dallas, TX: The Pragmatic Bookshelf, 2011 Perrotta, Paolo. Metaprogramming Ruby: Program Like the Ruby Pros. Dallas, TX: The Pragmatic Bookshelf, 2011 Thomas, Dave. The Ruby Object Model and Metaprogramming. Screen casts read by the author. Dallas, TX: The Pragmatic Bookshelf, 2011 Brady, David. Ruby Rouges: Episode 39, Programming Language Fundamentals. [Podcast], January 28, 2012 Pavalta, Ondrej (March 2, 2011) The Ruby Object Model: Data Structure in detail. From http://www.atalon.cz/rb-om/ruby-object- model/ The Ruby Object Model as Interpreted by Susan Muldowney [Video]. (June 13, 2011) From http://www.youtube.com/watch? v=UyAoUX6GYI8 McSpadden, Mark. Ruby Object Model [Tweet]. (August 22, 2011) From http://www.twitter.com, @markmcspadden Dearing, Jesse. Less Magic [Tweet]. (January 4, 2012) From http://www.twitter.com, @jessedearing Wednesday, March 7, 2012