1. Objects, Objects
Everywhere
Mike Pack
@zombidev

2. Let’s Talk Objects
Behavior
+
State

3. Let’s Talk Objects
Behavior
I’m a person, what can I do?
Walk
Talk
Eat
Could also be defined as:
Move Legs
Move Lips
Ingest Food

4. Let’s Talk Objects
Behavior
Level of abstraction matters!
Behavioral abstraction varies per domain.

5. Let’s Talk Objects
State
I’m a person, who am I currently?
Mike Pack
Male
Brown
Therefore, I have attributes:
Name
Gender
Hair Color

6. Let’s Talk Objects
State
States change
When I’m 70, my attributes might be:
Mike Pack
Male
Grey

7. Let’s Talk Objects
Behavior changes too!
I just learned to jump, now my behavior is:
Walk
Talk
Eat
Jump

8. Let’s Talk Objects
Behavior
+
State

9. HTML
<div id=”name”>
Mike
</div>
Is this an object?

10. Attribute
HTML Name
<div id=”name”>
Mike
</div>
Is this an object?

11. Attribute
HTML Name
<div id=”name”>
Mike
State
</div>
Is this an object?

12. Attribute
HTML Name
<div id=”name”>
Mike the beef?
Where’s State
</div>
Is this an object?

13. Attribute
HTML Name
<div id=”name”>
Mike behavior?
Where’s the State
</div>
Is this an object?

14. HTML
<div id=”name”
onclick=”...”>
Mike
</div>
Is this an object?

15. Attribute
HTML Name
<div id=”name”
onclick=”...”>
Mike Behavior!
</div> State
Is this an object?

16. HTML
HTML is object oriented
(albeit, not for purist)
HTML does not exhibit other properties of an OO systems:
- Inheritance
- Polymorphism
- etc

17. HTML
Don’t use onclick=”...”
However, without onclick, HTML does not exhibit behavior.

18. CSS
a{
color: red;
}
Is this an object?

19. CSS
Attribute
a{ Name
color: red;
}
Is this an object?

20. CSS
Attribute
a{ Name
color: red;
} State
Is this an object?

21. CSS
Attribute
a{ Name
color:the beef?
Where’s red;
} State
Is this an object?

22. CSS
a{
color: red;
&:hover {
color: blue;
}
}
Is this an object?

23. Attribute CSS
Name a {
color: red; Behavior!
&:hover {
color: blue;
}
State
}
Is this an object?

24. CSS
a{
Behavior color: red; State
&:hover { Change
color: blue;
}
}
Behavior changes state.

25. CSS
CSS is object oriented
(not for purist)
CSS does not exhibit other properties of an OO systems:
- Inheritance
- Polymorphism
- etc

26. JavaScript
var book = {
title: “The Art of
War”
};
Is this an object?

27. Attribute
Name
JavaScript
var book = {
title: “The Art of
War”
};
Is this an object?

28. Attribute
Name
JavaScript
var book = {
title: “The Art of
War” State
};
Is this an object?

29. Attribute
Name
JavaScript
var book = {
title: “The Art of
Where’s the beef?
War” State
};
Is this an object?

30. Attribute
Name
JavaScript
var book = {
title: “The Art of
Where’s the beef?
It’sWar”
implicit! State
};
Is this an object?

31. JavaScript
var book = {
title: “The Art of War”,
constructor: function() {...},
hasOwnProperty: function() {...},
...
};
Implicit behavior.

32. JavaScript
JavaScript is object oriented
(of course)

33. JavaScript
It’s not entirely object oriented
JavaScript has primitives, too.

34. JavaScript
If it’s an object, typeof knows
typeof {} === ‘object’ //=> true

35. JavaScript
Integers are not objects
typeof 1 === ‘object’ //=> false

36. JavaScript
undefined is not an object
typeof undefined === ‘object’ //=> false

37. JavaScript
Literals are not always primitives
typeof [] === ‘object’ //=> true

38. JavaScript
typeof might not return object
typeof true === ‘object’ //=> false
typeof true === ‘boolean’ //=> true
But booleans are objects!
new Boolean(1).valueOf() === true //=> true

39. JavaScript
Careful, typeof can bite
typeof null === ‘object’ //=> true
new Null() //=> error

40. Ruby
1
Is this an object?

41. Ruby State
(accessor)
1
1.real #=> 1
Is this an object?

42. Ruby State
(accessor)
1
1.real #=> 1
1 + 1 #=> 2
Is this an object?

43. Ruby State
1 (accessor)
1.real #=> 1
Behavior 1 + 1 #=> 2
1.+(1) #=> 2
Is this an object?

44. Ruby
Ruby is object oriented

45. Ruby
Everything is an object

46. Ruby
Literal arrays are new objects
[].object_id #=> 70318249770140
[].object_id #=> 70318249594160

47. Ruby
Literal strings are new objects
‘slurpy’.object_id #=> 70318249561400
‘slurpy’.object_id #=> 70318249500340

48. Ruby
Literal hashes are new objects
{}.object_id #=> 7019206373870
{}.object_id #=> 70192063701240

49. Ruby
Literal regexs are new objects
//.object_id #=> 70192063385520
//.object_id #=> 70192067965040

50. Ruby
Literal ranges are new objects
(1..2).object_id #=> 70192067946460
(1..2).object_id #=> 70192067921120

51. Ruby
Not everything creates a new
object
Ruby has singleton objects (objects instantiated once).

52. Ruby
nil is a singleton
nil.object_id #=> 4
nil.object_id #=> 4

53. Ruby
booleans are singletons
false.object_id #=> 0
false.object_id #=> 0
true.object_id #=> 2
true.object_id #=> 2

54. Ruby
Numbers are singletons
1.object_id #=> 3
1.object_id #=> 3

55. Ruby
um s
xn
Fi Numbers are singletons
1.object_id #=> 3
1.object_id #=> 3

56. Ruby
Bignums are not singletons
4611686018427387904.object_id #=>
70192063730740
4611686018427387904.object_id #=>
70192063508580

57. Ruby
Bignums are not singletons
4611686018427387904.object_id #=>
70192063730740
4611686018427387904.object_id #=>
70192063508580
Why 4611686018427387904?

58. bytes to store
Ruby integer
bytes = 0.size #=> 8

59. bytes to store
Ruby integer
bytes = 0.size #=> 8
8 bits per byte
bits = bytes * 8 #=> 64
64 bit machine

60. bytes to store
Ruby integer
bytes = 0.size #=> 8
8 bits per byte
bits = bytes * 8 #=> 64
64 bit machine
1 bit for sign
+ 1 bit for Ruby
2 ** (bits - 2) #=>
4611686018427387904

61. Ruby
4611686018427387904
Bignum
Different objects.
4611686018427387904 - 1
Fixnum
Singleton object.

62. Ruby
Why does nil have object_id of 4?
1 have object_id of 3?
true have object_id of 2?

63. Ruby
Because Matz says so
false.object_id #=> 0
0.object_id #=> 1
true.object_id #=> 2
1.object_id #=> 3
nil.object_id #=> 4
2.object_id #=> 5

64. Ruby
Find by object_id
ObjectSpace._id2ref(0) #=> false
ObjectSpace._id2ref(1) #=> 0
ObjectSpace._id2ref(2) #=> true
ObjectSpace._id2ref(3) #=> 1
ObjectSpace._id2ref(4) #=> nil
ObjectSpace._id2ref(5) #=> 2
ObjectSpace._id2ref(6) #=> error
ObjectSpace._id2ref(7) #=> 3
ObjectSpace._id2ref(8) #=> error

65. Ruby
Negative object_ids
-1.object_id #=> -1
-2.object_id #=> -3
-3.object_id #=> -5

66. Objects.useful? # => true

67. Objects.useful? # => true
Consistent modeling across the stack.

68. Objects.useful? # => true
Helpful in representing the real world.

69. Objects.useful? # => true
Fun and expressive.

70. Thanks!
@zombidev