In defense of object-oriented programming - How and why you should use object oriented programming for your next project. This talk is for PHP programmers who are just learning about object oriented code, who cling to old excuses ("object oriented code is slower"), or who are otherwise unconvinced of its usefulness. Concrete real-world examples of common scenarios and challenges that programmers face will be presented, and how taking an object oriented approach is better than a procedural one in most cases. Copious code examples in both object oriented and procedural approaches will be provided throughout, and the differences and benefits of the object oriented approach will be explained.

1. Object Oriented Apologetics Vance Lucas CodeWorks 2009 Dallas September 27, 2009

2. What? 2 Not an apology Greek root - apologia (απολογία) - “speaking in defense” To defend the use of, and provide rational reasoning for

3. 3 Who is it for? For People Who: Are “on the fence” about OOP vs procedural Are unconvinced of the usefulness of OOP Want to learn WHY they should learn about OOP

4. 4 Purpose: To Get You Hooked on OOP

5. 5 NO Academic or Mundane Examples

6. 6 No Shapes, Cars, Fruit, or Bicycles

7. <?phpclass myClass { public function myClass(){ } public function echoMe(){ echo 'me'; } } $mine=new myClass(); $mine->echoMe(); ?> 7 No “Hello World” Scripts

8. So… Why OOP?

9. Polymorphism I nheritance E ncapsulation 9

10. 10 Polymorphism

11. Making things that are not the same look the same Relies on a defined interface Inheritance is probably the most used method The ability of type A to be used like type B Think: Interchangeable types or components 11 Polymorphism

12. 12 Real World: Different Implementations

13. 13 Procedural - Inline

14. 14 Object-oriented – Polymorphic Interface

15. 15 Inheritance

16. Extend from a parent class “is-a” relationship Creates hierarchal relationship Get functionality for free Global changes are easier Inherits all functions and properties from parent Think: A is a B, with a few differences 16 Inheritance

17. 17 Controller: Zend Framework

18. 18 Model: phpDataMapper

19. 19 Warning: Keep Hierarchy Shallow

20. 20 Encapsulation

21. Hide specific implementation details Reveal only methods and properties required to interact with the object Limits interdependencies between components Think: Separation of responsibilities 21 Encapsulation

22. 22 Payment Interface – Exposed Methods

23. 23 Planetoids (by Micah Jones)

25. Different: velocities, sizes, shapes, rotations, color, and fragment pieces

26. All the code and math calculations for movement are encapsulated behind ‘move()’

27. Allows different types of objects and asteroids to be treated the same in code – “polymorphically”24 Planetoids: Code Abstraction

28. Other OOP-Only Features? 25

29. Lazy-Loading

30. Uses __get() “magic” method in PHP5 object model Also uses SPL interfaces to fire query on: count() foreach() Used as a hook to retrieve related rows on call Caches results so only 1 query is fired Can eliminate N+1 query problem by mapping 27 Lazy-Loading: OOP Only

31. Classes are actually custom types Can type-hint for classes or interfaces PHP Standard types: string, int, float, boolean, array, object, null resource 28 Custom Type Creation & Type-Hinting

32. Other Reasons TO Use OOP?

33. Easily group related properties/data Avoid using globals or passing/returning arrays Suppress errors ala ‘undefined index’ More? Convenience (a.k.a. Laziness) 30

34. Request object: Why not $_POST? Data comes from multiple sources POST/GET, XML, JSON, etc. Other functions isAjax(), isPost(), etc. Sanitizing user input Session object: Why not $_SESSION? More options for saving/storing Database, separate server, memcached, etc. 31 Request / Session Objects

35. 32 Request Object: Convenience, too!

36. Need an Example?

38. Simple products, no options, stock, etc.

39. Simple checkout, no user accounts

40. Authorize.net integration

41. UPS rate quotes

42. Admin backend

43. Order fulfillment

45. Simple Checkout 36

46. 37 Simple UPS Integration

47. So far it’s OK It works We finished and worked quickly 38 Status Check

48. 39 Client Message I talked to my next door neighbor’s cousin’s brother’s niece yesterday, and he says all the serious online stores have regular sales. That’s something I can do too, right? - Bob

49. 40 Product Sales

50. 41 New Code for Product Sale

51. We also have to add this code to the admin backend for customer invoices. And to the email reciepts Sin of code duplication Code smell 42 Thoughts

52. 43 Client Message Hey,I was at the grocery store yesterday and my daughter got 2 candy bars for $1, when they were originally $0.75 each. I know that if I am able to do this, I’ll get a lot of sales and it will make me rich. I need to be able to do this. - Bob

53. 44 Multi-Quantity Discounts

54. New Code, Again 45

55. We also have to add this code to the admin backend and other places again. Sin of code duplication We could use procedural functions for this Where would we put them? What responsibilities do they have? 46 Thoughts

56. 47 What about the future?

57. 48 Employee Discounts

58. 49 Switching to FedEx

59. Stock Checking 50

60. Clearly, as the project grows, it will become a maintenance nightmare if we continue on the current path. We don’t want our code to be the running joke of the PHP community. 51 We need something better

61. 52

62. 53 Use the right tool for the right job

63. 54 OOP: Right tool for this job

64. Create a Cart class to store items Encapsulate the pricing logic in an Item class Single place to change the code Item is responsible for knowing it’s price (?) What does this imply? 55 Thoughts

65. 56 Possible Code Changes

66. Still storing cart in session, but now we can change it later when we need to scale Cart gets item price so it can check quantities Cart is responsible for knowing other items in cart Better separation of responsibility It’s not the job of the display logic to calculate the item’s price or apply discounts What about changing to FedEx? 57 Thoughts

67. 58 Re-factor it into two classes

68. Package is responsible for knowing it’s own dimensions and weight Quote is responsible for fetching a live rate quote from a carrier API service Always think in terms of responsibility What code is responsible for what functions? Where does it go in my app? Is this code doing too much? 59 Thoughts

69. 60 Think about how an assembly line works

70. OOP Myths and Misconceptions

71. 62 Myth #1: OOP is about code re-use

72. 63 Truth: Re-useable code is a by-product of good OO

73. 64 Problem: There are lots of ways to make re-useable code that are not object-oriented nor good. It’s a bad goal.

74. <Code with functions and includes – re-useable> 65 Functions are re-useable

75. 66 Specific implementations are re-useable

76. <UPS-Specific API Code> or <Payment Gateway-specific API Code> 67 Soft interfaces are re-useable

77. You must set goals that will help direct you to your desired outcome Goals narrow attention and direct efforts to goal-relevant activities, and away from perceived undesirable and goal-irrelevant actions Re-use as a goal does not help you write good OO code. Re-use is a by-product of good OO. 68 Point: Set Good Goals

78. 69 Myth #2: Objects should always be modeled after real-world objects when possible

79. 70 Truth: Objects should be modeled and built based on what you need to complete your task

80. 71 Problem: Real-world object models are almost never useful in code

81. 72 Real-World Objects Change

82. 73 You are modeling things that don’t exist

83. 74

84. 75 Myth #3: Everything should be objects

85. 76 Truth: Make objects for only what you need to. Most of the time this is data. Don’t over-complicate your code when it’s not necessary.

86. 77 Problem: Not everything your code does can be easily represented with an object

87. 78 Application Flow MVC diagram for XEROX PARC 1978-79

88. 79

89. Programming PHP for over 10 years Web: http://www.vancelucas.com Twitter: @vlucas Email: vance@vancelucas.com GitHub: http://github.com/vlucas Photo Set: http://www.flickr.com/photos/30728345@N05/galleries/72157622318592067/ 80 Vance Lucas