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