A talk presented in RubyConf India 2010 at Bangalore, India. It revisits the role of objects and classes in Ruby OOP, and encourages programmers to discover a new approach to OOP.

1. Ruby OOP: Objects over Classes Aman King king@thoughtworks.com RubyConf India 2010

2. What is OOP?

3. What is a class?

4. What is an object?

5. But before the serious stuff …

6. Detouring through a comic book universe … Image copyrighted by respective owners Source: http://www.comics.org/

7. Coming back …

8. What is an object?

9. Something that takes birth …

10. exhibits some behavior …

11. interacts with other objects …

12. and finally dies off or is simply forgotten …

13. all in an effort to solve a problem.

14. What is a class?

15. A container for related behavior …

16. that a new object can start off with.

17. A class itself is an object …

18. used to create other objects.

19. When creating a new object, a class calls the object’s private initialize method.

20. Typically a class is named …

21. referenced via a global constant variable.

22. A class object can have singleton methods added to it.

23. These singleton methods can be invoked wherever the class object is accessible …

24. aka “class-level methods”.

25. Why use classes?

26. Some possible reasons

27. An object remembers the class used to create it …

28. explicit type checking using kind_of? …

29. implicit type checking using case syntax …

30. implicit type checking using rescue syntax.

31. A class can build on other classes: inheritance.

32. A class can share state across multiple objects: @@class_variables.

33. Some good reasons

34. A named container of behavior can have more behavior added to it.

35. Any added behavior becomes part of all objects created by that class.

36. A class can represent a common pattern of initialization.

37. Classes improve readability and maintainability.

38. What a class is not?

39. The fundamental building block of an application.

40. A strong data type.

41. An enforcement of contract or limitations on how objects can behave.

42. Ruby’s object focus

43. Classes are objects.

44. No static method-lookup tables: chain of ancestors.

45. Singleton methods.

46. Private access modifier is object-level.

47. Duck typing.

48. Finding hints in the real world …

49. Objects over classes: Consequences

50. Classes and hierarchies no longer limit you.

51. Think through the usage of class-level methods and variables: globals?

52. Understanding meta-programming is easier.

53. Effective and confident use of meta-programming.

54. Final words

55. Objects are first-class citizens.

56. Classes are useful but secondary.

57. Thank you king@thoughtworks.com http://www.wikyblog.com/AmanKing