1
00:00:00,260 --> 00:00:01,720
Okay, so let me see if

2
00:00:01,720 --> 00:00:07,930
anything changed after we did this last modification.

3
00:00:07,930 --> 00:00:09,530
Acutally, there is someting that I would like

4
00:00:09,530 --> 00:00:12,120
to do here. Because looking at this a little

5
00:00:12,120 --> 00:00:15,560
bit more, I noticed that there are two

6
00:00:15,560 --> 00:00:18,760
attributes, renewed and due date. That we have in

7
00:00:18,760 --> 00:00:21,640
loanable Item, right? But they don't seem to

8
00:00:21,640 --> 00:00:25,590
be really, attributes or characteristics of loanable Item.

9
00:00:25,590 --> 00:00:29,150
They're more of the characteristics of the association between the

10
00:00:29,150 --> 00:00:31,450
Loanable Item and the patron. Wouldn't you agree?

11
00:00:32,470 --> 00:00:34,230
>> Well, yeah, it's not like you could

12
00:00:34,230 --> 00:00:37,644
only renew a book once in it's entire history.

13
00:00:37,644 --> 00:00:41,220
>> Right. Exactly, exactly. So, that's why what l like

14
00:00:41,220 --> 00:00:43,970
to do is I would like to move those out of loanable

15
00:00:43,970 --> 00:00:48,020
item. And actually there is a construct that we can use

16
00:00:48,020 --> 00:00:50,710
to express this. It's called, we haven't seen it yet, but it's

17
00:00:50,710 --> 00:00:52,780
a special kind of class. It's called an association

18
00:00:52,780 --> 00:00:55,480
class. So, it's a class that is connected to

19
00:00:55,480 --> 00:00:57,730
a specific association. So what we can do

20
00:00:57,730 --> 00:01:00,730
here, we can create this class, which I'm going to

21
00:01:00,730 --> 00:01:05,200
call checked out. I'm going to, associate it with

22
00:01:05,200 --> 00:01:09,520
this, association. I'm going to connect it with this association. And

23
00:01:09,520 --> 00:01:11,620
then I'm going to move the due date and the

24
00:01:11,620 --> 00:01:16,300
renewed attributes From the LoanableItem here in this checked

25
00:01:16,300 --> 00:01:18,520
out class. So in this way, seems to me that

26
00:01:18,520 --> 00:01:20,910
it makes it very explicit for somebody looking at this

27
00:01:20,910 --> 00:01:25,530
class diagram, that these characteristics are characteristics of the loan,

28
00:01:25,530 --> 00:01:28,200
and not of the elements involved in the loan.

29
00:01:28,200 --> 00:01:33,410
>> Can you do the same thing with Fine, isn't Fine a property of the

30
00:01:33,410 --> 00:01:36,740
loan? Yeah, actually is right because

31
00:01:36,740 --> 00:01:39,120
a fine is a fine for a specific loan, right?

32
00:01:39,120 --> 00:01:39,910
>> That's correct.

33
00:01:39,910 --> 00:01:41,950
>> Okay, so yeah. Then we can do that.

34
00:01:41,950 --> 00:01:45,900
We don't need to represent fine as a class, we can just transform

35
00:01:45,900 --> 00:01:49,460
that into an attribute that we can put into the checked out association class.

36
00:01:49,460 --> 00:01:50,560
>> Gotcha.

37
00:01:50,560 --> 00:01:52,760
>> Anything else?

38
00:01:52,760 --> 00:01:57,990
>> Yeah. It occurred to me that there's another thing that happens in one

39
00:01:57,990 --> 00:02:00,260
of my scenarios, I put down

40
00:02:00,260 --> 00:02:02,770
about the patron actually returning an item.

41
00:02:02,770 --> 00:02:07,620
>> Right. Okay, so we would probably need an additional operation,

42
00:02:07,620 --> 00:02:08,550
I guess, for the patron.

43
00:02:08,550 --> 00:02:08,990
>> Right.

44
00:02:08,990 --> 00:02:11,310
>> So, okay, so what I'm going to do, that's pretty easy

45
00:02:11,310 --> 00:02:15,350
to do, I'm just going to add the return operation here in the

46
00:02:15,350 --> 00:02:19,310
patron, and when that happens, that will mean that I'll get rid

47
00:02:19,310 --> 00:02:23,490
of this association class because the item is returned. Is that right?

48
00:02:23,490 --> 00:02:27,060
>> Well, what happens if somebody drops the

49
00:02:27,060 --> 00:02:29,400
book in the book drop, but doesn't pay the,

50
00:02:29,400 --> 00:02:31,050
if it's overdue and doesn't pay the fine?

51
00:02:31,050 --> 00:02:32,700
Will that get rid of the information about what

52
00:02:32,700 --> 00:02:33,040
they owe?

53
00:02:33,040 --> 00:02:37,960
>> Oh, I see. So you can have the item being available, but you still

54
00:02:37,960 --> 00:02:42,510
want to know whether there is any pending fines on the book.

55
00:02:42,510 --> 00:02:44,390
>> Uh-huh, and how much those fines are.

56
00:02:44,390 --> 00:02:46,340
>> And how do you compute how much it is?

57
00:02:47,420 --> 00:02:52,710
>> It's how many days it was, from the time it was

58
00:02:52,710 --> 00:02:58,170
due, to when they returned it. I see. OK.

59
00:02:58,170 --> 00:03:00,380
So you know what we can do? I think

60
00:03:00,380 --> 00:03:03,690
we can put an additional attribute in the checked out

61
00:03:03,690 --> 00:03:07,190
class and I'm going to call it when returned and

62
00:03:07,190 --> 00:03:10,200
that item will have either a special value or it

63
00:03:10,200 --> 00:03:12,040
will contain the date in which the book was

64
00:03:12,040 --> 00:03:14,520
returned. So in this way you should be able to

65
00:03:14,520 --> 00:03:18,040
keep this in the system until it's paid, and also to compute

66
00:03:18,040 --> 00:03:19,970
how much the fine is. Is that working?

67
00:03:19,970 --> 00:03:23,210
>> So the special value is for a normal situation when they

68
00:03:23,210 --> 00:03:25,880
haven't, they don't owe anything and haven't returned it yet.

69
00:03:25,880 --> 00:03:28,080
>> Exactly so that will tell us that,

70
00:03:28,080 --> 00:03:29,970
that the loan is still active basically.

71
00:03:29,970 --> 00:03:30,500
>> Great.

72
00:03:30,500 --> 00:03:31,480
>> Does that work for you?

73
00:03:31,480 --> 00:03:35,200
>> Yes. And you know, I like this. I mean, I feel pretty good

74
00:03:35,200 --> 00:03:38,490
about it. I think we have a nice class diagram. So what I'd like to

75
00:03:38,490 --> 00:03:43,280
do is just go off and clean it up a little bit, and put it

76
00:03:43,280 --> 00:03:48,640
in an IDE so I can pretty print it and rearrange things a little bit.

77
00:03:48,640 --> 00:03:50,080
And then I'd like to sit down again and

78
00:03:50,080 --> 00:03:52,730
just go through it for a last time. And

79
00:03:52,730 --> 00:03:54,900
for some final considerations. So if you don't mind

80
00:03:54,900 --> 00:03:56,880
we will take a ten minute break and reconvene here.

81
00:03:56,880 --> 00:03:57,500
>> That's fine.

82
00:03:57,500 --> 00:03:57,990
>> Alright.