1
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‫Let's now handle the error

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‫that occurs when we try to create duplicate fields

3
00:00:06,140 --> 00:00:09,633
‫for fields that are actually supposed to be unique.

4
00:00:11,110 --> 00:00:12,210
‫And so, remember,

5
00:00:12,210 --> 00:00:13,940
‫that this is the type of error

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‫that we get.

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00:00:14,900 --> 00:00:16,673
‫So, we tried to create a new tour

8
00:00:16,673 --> 00:00:19,000
‫with a name that already exists

9
00:00:19,000 --> 00:00:21,550
‫and the name fields is supposed to be unique

10
00:00:21,550 --> 00:00:23,670
‫and so we get this error.

11
00:00:23,670 --> 00:00:25,250
‫Now this error here doesn't have

12
00:00:25,250 --> 00:00:27,210
‫a name property, okay?

13
00:00:27,210 --> 00:00:29,071
‫And that's because, as I mentioned before,

14
00:00:29,071 --> 00:00:30,910
‫it is actually not an error

15
00:00:30,910 --> 00:00:32,720
‫that is caused by a Mongoose.

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00:00:32,720 --> 00:00:35,000
‫But instead, really, by the underlying

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00:00:35,000 --> 00:00:37,830
‫MongoDB driver, okay?

18
00:00:37,830 --> 00:00:39,140
‫And so, what we're gonna do

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00:00:39,140 --> 00:00:40,734
‫to identify this error

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‫is use this 11,000 code here.

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00:00:45,580 --> 00:00:46,413
‫All right?

22
00:00:47,970 --> 00:00:51,263
‫So, we have one handler for the CastError.

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00:00:51,263 --> 00:00:54,190
‫Let's now create one for the case

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00:00:54,190 --> 00:00:55,823
‫that we have that error.code,

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00:00:56,837 --> 00:01:00,673
‫.code equal to 11,000.

26
00:01:01,640 --> 00:01:04,138
‫So in that case, all error should be equal

27
00:01:04,138 --> 00:01:08,833
‫to the error returns from handleDuplicateFields

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00:01:10,610 --> 00:01:12,610
‫and again, I'm adding DB here

29
00:01:12,610 --> 00:01:15,983
‫just so we know that this has to do with our database.

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00:01:16,940 --> 00:01:18,160
‫All right?

31
00:01:18,160 --> 00:01:22,383
‫And, so let's now actually then create this function.

32
00:01:29,470 --> 00:01:32,900
‫And now, the message that we're gonna send

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00:01:34,900 --> 00:01:37,470
‫is this one so let's create it here.

34
00:01:37,470 --> 00:01:38,993
‫And so I want it to say,

35
00:01:43,220 --> 00:01:46,090
‫Duplicate field value, and then hear the name

36
00:01:46,090 --> 00:01:49,503
‫of that value, so let's put that to x for now.

37
00:01:50,760 --> 00:01:53,160
‫We will generate that a bit later.

38
00:01:53,160 --> 00:01:57,113
‫So please use another value.

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00:01:58,170 --> 00:01:59,030
‫All right?

40
00:01:59,030 --> 00:02:01,120
‫And so in the case that we just saw,

41
00:02:01,120 --> 00:02:04,093
‫this x here should be called the Forest Hiker.

42
00:02:05,730 --> 00:02:07,410
‫So basically, what we're trying to get

43
00:02:07,410 --> 00:02:11,090
‫out of this error message string here

44
00:02:11,090 --> 00:02:13,577
‫is this, "The Forest Hiker."

45
00:02:14,569 --> 00:02:16,280
‫So that is the duplicate value

46
00:02:16,280 --> 00:02:18,040
‫that we want to send to the client

47
00:02:18,040 --> 00:02:20,100
‫so that they can now correct it

48
00:02:20,100 --> 00:02:22,040
‫and create another name.

49
00:02:22,040 --> 00:02:23,595
‫So, how can we actually extract

50
00:02:23,595 --> 00:02:26,120
‫this piece of the string here?

51
00:02:26,120 --> 00:02:28,520
‫Well, we're gonna use a regular expression

52
00:02:28,520 --> 00:02:30,640
‫to, basically, as I just said,

53
00:02:30,640 --> 00:02:33,170
‫find the text that is between quotes.

54
00:02:33,170 --> 00:02:35,520
‫'Cause here in this string, all we have really

55
00:02:35,520 --> 00:02:37,670
‫to identify this text here,

56
00:02:37,670 --> 00:02:40,460
‫so to find it, is these quotes.

57
00:02:40,460 --> 00:02:41,293
‫All right?

58
00:02:41,293 --> 00:02:43,010
‫And now, as you already know,

59
00:02:43,010 --> 00:02:45,670
‫regular expressions can be really tough.

60
00:02:45,670 --> 00:02:47,840
‫And so I usually just Google them

61
00:02:47,840 --> 00:02:50,273
‫and so let me show you how I actually do that.

62
00:02:53,280 --> 00:02:55,250
‫In this case, I would simply search

63
00:02:55,250 --> 00:03:00,250
‫for regular expression match text between quotes.

64
00:03:05,620 --> 00:03:08,660
‫And then usually it's right the first result.

65
00:03:08,660 --> 00:03:11,250
‫And then down here we have the result

66
00:03:11,250 --> 00:03:14,698
‫and so we can use simply this regular expression.

67
00:03:14,698 --> 00:03:17,150
‫Now I see that we have down here this here.

68
00:03:17,150 --> 00:03:19,270
‫This also works and it's easier to read.

69
00:03:19,270 --> 00:03:21,100
‫And it has a bunch of up votes

70
00:03:21,100 --> 00:03:23,280
‫and so we simply can use this one.

71
00:03:23,280 --> 00:03:25,290
‫So that should work as well.

72
00:03:25,290 --> 00:03:29,870
‫So let's copy it and let's go back to our code,

73
00:03:29,870 --> 00:03:32,493
‫and say that our value,

74
00:03:34,440 --> 00:03:37,663
‫so const value is equal to the error.ermsg,

75
00:03:40,990 --> 00:03:45,990
‫so remember, that that was the name of the property.

76
00:03:46,000 --> 00:03:48,820
‫So, errmsg. So again, that's because

77
00:03:48,820 --> 00:03:51,010
‫this is an error created by Mongo

78
00:03:51,010 --> 00:03:53,383
‫and so these is slightly different names.

79
00:03:54,410 --> 00:03:55,243
‫Okay?

80
00:03:55,243 --> 00:03:57,890
‫So we have this string and now here we want to match

81
00:03:57,890 --> 00:03:59,973
‫our regular expression.

82
00:04:02,140 --> 00:04:04,260
‫So, match, and then in JavaScript,

83
00:04:04,260 --> 00:04:07,623
‫a regular expression is always between two slashes.

84
00:04:08,530 --> 00:04:12,220
‫Then paste it here what we just got from Stack Overflow

85
00:04:14,450 --> 00:04:16,000
‫and let's actually take a look.

86
00:04:22,260 --> 00:04:24,600
‫So, we're running already in production.

87
00:04:24,600 --> 00:04:27,340
‫Right now we will not send back any response.

88
00:04:27,340 --> 00:04:30,203
‫All I want to do now is to take a look at the value.

89
00:04:31,870 --> 00:04:36,870
‫So, if I sent this now we get this weird response here.

90
00:04:37,870 --> 00:04:40,910
‫And again, that's because we're not sending any error.

91
00:04:40,910 --> 00:04:44,213
‫But for now I was really just interested in the value.

92
00:04:45,540 --> 00:04:46,660
‫And so this, what we see here

93
00:04:46,660 --> 00:04:48,980
‫in the log now is that value.

94
00:04:48,980 --> 00:04:51,163
‫And actually it is an array.

95
00:04:52,030 --> 00:04:55,830
‫But what we're interested in is actually this string here.

96
00:04:55,830 --> 00:04:58,550
‫So it did actually match all the text

97
00:04:58,550 --> 00:05:00,670
‫that was between strings and so,

98
00:05:00,670 --> 00:05:01,970
‫we can say that it worked.

99
00:05:03,680 --> 00:05:06,720
‫So our regular expression worked.

100
00:05:06,720 --> 00:05:08,370
‫Now, all we have to say is that we want

101
00:05:08,370 --> 00:05:10,970
‫the first element of that array.

102
00:05:10,970 --> 00:05:12,960
‫So, element zero.

103
00:05:12,960 --> 00:05:16,280
‫And now, let's actually go ahead and return

104
00:05:16,280 --> 00:05:20,590
‫or new AppError, so new AppError,

105
00:05:20,590 --> 00:05:22,560
‫paste in the message,

106
00:05:22,560 --> 00:05:25,993
‫and again the 400 status code for a bad request.

107
00:05:27,999 --> 00:05:29,570
‫And so let's now try that again.

108
00:05:29,570 --> 00:05:31,820
‫Again, we are still running a production

109
00:05:31,820 --> 00:05:34,550
‫and so that code should now run.

110
00:05:34,550 --> 00:05:37,423
‫And of course, we tried to replace our x.

111
00:05:40,400 --> 00:05:42,613
‫Of course, we now want our value here.

112
00:05:46,750 --> 00:05:49,327
‫And so, now we get duplicate field value,

113
00:05:49,327 --> 00:05:51,110
‫"The Forest Hiker."

114
00:05:51,110 --> 00:05:51,970
‫Perfect.

115
00:05:51,970 --> 00:05:54,140
‫And now, next up, in the next video

116
00:05:54,140 --> 00:05:57,330
‫we will then handle the last of the three errors

117
00:05:57,330 --> 00:05:59,083
‫which are the validation errors.