1
00:00:02,300 --> 00:00:08,720
Now with our basic interactions setup, we have to optimize our code a bit and move it into a more realistic

2
00:00:08,720 --> 00:00:09,910
setup.

3
00:00:10,080 --> 00:00:17,660
Now for that more realistic setup, I'll create a new file next to app.js and I'll name it database or

4
00:00:17,980 --> 00:00:20,500
db.js.

5
00:00:20,570 --> 00:00:29,250
Now in this file, I will import mongodb here and then I'll write some code here which gives me a

6
00:00:29,250 --> 00:00:34,920
nice utility script to set up a connection to the database and then get access to the established connection.

7
00:00:35,700 --> 00:00:36,410
For this, I'll

8
00:00:36,540 --> 00:00:39,860
first of all create a new constant, 

9
00:00:39,940 --> 00:00:46,890
initDb which simply points at a function which receives a callback,

10
00:00:46,950 --> 00:00:49,660
so another function it can execute as an argument

11
00:00:50,390 --> 00:01:02,740
and here additionally in that file, I'll add a variable with let _db, it has no initial value. Inside

12
00:01:02,740 --> 00:01:03,290
of initDb,

13
00:01:03,310 --> 00:01:11,530
I'll check if db is uninitialized and if it is not uninitialized, so if this returns true which

14
00:01:11,530 --> 00:01:13,560
only happens if it is initialized,

15
00:01:15,070 --> 00:01:21,670
then I'll simply log database is already initialized

16
00:01:24,200 --> 00:01:26,460
and I'll just return my callback,

17
00:01:26,460 --> 00:01:27,860
so I basically call the callback

18
00:01:27,890 --> 00:01:34,220
I basically expect to get a function as an argument so to say and I'll execute that function here and I pass null

19
00:01:34,220 --> 00:01:38,180
as a first argument because my callback will receive an error as a first argument

20
00:01:38,210 --> 00:01:40,030
and I don't want to throw an error here,

21
00:01:40,040 --> 00:01:42,010
it's fine that we already are connected,

22
00:01:42,020 --> 00:01:44,840
so I just return the existing database

23
00:01:44,840 --> 00:01:50,300
but of course this is a case we can't reach right now because we have no code to actually store something

24
00:01:50,300 --> 00:01:51,840
in _db.

25
00:01:52,130 --> 00:01:53,490
So this is what happens now,

26
00:01:53,960 --> 00:02:02,000
I will create my constant mongo client here and use mongodb mongo client to well get access to

27
00:02:02,000 --> 00:02:03,400
the client.

28
00:02:03,420 --> 00:02:11,290
I'll also create a new constant, mongoDbUrl

29
00:02:11,310 --> 00:02:13,730
and that will be my connection

30
00:02:13,740 --> 00:02:14,410
url,

31
00:02:14,490 --> 00:02:20,000
so basically the url I'm using in the products.js file right now here for the connect method.

32
00:02:20,140 --> 00:02:26,280
This string, that is what I copy and that is what I move into the db.js file and which I store here

33
00:02:26,460 --> 00:02:30,740
as a string as about. Now back in initDb,

34
00:02:30,740 --> 00:02:36,670
I will use the mongo client here and call connect and use that mongoDbUrl,

35
00:02:36,680 --> 00:02:41,850
so basically the same code I have in products.js. Now by the way,

36
00:02:41,850 --> 00:02:45,200
you can also, that should have a lowercase l,

37
00:02:45,330 --> 00:02:50,180
you can also pass a second argument where you configure this connection here.

38
00:02:50,190 --> 00:02:54,270
Now this is a bit more advanced and you should check out the official driver docs to learn what you

39
00:02:54,270 --> 00:02:55,530
can configure here,

40
00:02:55,710 --> 00:02:59,650
the default settings should be fine and they are fine for us here.

41
00:03:00,910 --> 00:03:07,790
So I will just connect like this and then here of course, we have a promise then and catch are

42
00:03:07,810 --> 00:03:13,260
therefore functions we can use here. Now in catch, we'll get any error that occurs during the connection

43
00:03:13,760 --> 00:03:22,750
and therefore here in the error case, I will execute my callback and pass that error as the first argument

44
00:03:22,840 --> 00:03:28,480
because I mentioned that the callback, the function I receive here, will be a function I call and I expect

45
00:03:28,480 --> 00:03:34,060
to whoever who passed this function to me to implement this function in a way that it is able to handle

46
00:03:34,060 --> 00:03:36,980
the first argument as a potential error.

47
00:03:37,360 --> 00:03:43,390
So that's the worse, the bad case, the good case is that we are successful so that we do it successfully

48
00:03:43,390 --> 00:03:44,230
connect

49
00:03:44,230 --> 00:03:48,190
and in this case, I get access to the client here in the then block,

50
00:03:48,310 --> 00:03:51,050
so the logic is the same as in the products.js file.

51
00:03:51,400 --> 00:03:56,210
So this client here allows me to then simply store the database,

52
00:03:56,260 --> 00:03:59,540
so db is then equal to client.db,

53
00:03:59,950 --> 00:04:07,280
so this gives me access to the database which was created.

54
00:04:07,360 --> 00:04:11,750
So now I have some method which I can execute to establish a connection,

55
00:04:11,770 --> 00:04:18,130
I'll now create a second constant in the same file which I'll name getDb to get access to this established database

56
00:04:18,130 --> 00:04:19,740
connection,

57
00:04:19,790 --> 00:04:25,440
whoops, it should be written like this, will also be an arrow function

58
00:04:25,880 --> 00:04:30,090
and here I simply return _db.

59
00:04:30,180 --> 00:04:31,870
However first of all, I'll quickly add an

60
00:04:32,000 --> 00:04:34,330
if check, if not _db so

61
00:04:34,370 --> 00:04:44,000
if this is uninitialized, then I'll throw an error where I say database not initialized.

62
00:04:45,120 --> 00:04:46,330
So now I have two functions

63
00:04:46,360 --> 00:04:53,430
in here, initDb to establish a connection and getDb to get access to an existing connection. How

64
00:04:53,430 --> 00:04:54,890
do I use these now?

65
00:04:55,350 --> 00:05:00,540
Well in app.js which is the first file that gets executed when we start up our server,

66
00:05:00,810 --> 00:05:06,570
I can remove that mongodb import I have there and instead, I can add an import to my database

67
00:05:07,230 --> 00:05:08,480
utility file, 

68
00:05:08,640 --> 00:05:15,150
so I'll just name it db and I do import my own file by typing require./db and you can omit

69
00:05:15,180 --> 00:05:15,620
the

70
00:05:15,630 --> 00:05:17,460
.js

71
00:05:17,460 --> 00:05:23,060
Now here before I call listen, I will call db

72
00:05:23,300 --> 00:05:29,500
and then what? Well I need to call the functions that are in that file and to make these functions callable,

73
00:05:29,600 --> 00:05:38,180
I add module exports at the end and I'll export an object here and that object will receive initDb

74
00:05:38,420 --> 00:05:44,630
and getDb and this syntax simply creates keys called initDb and getDb which receives their

75
00:05:44,630 --> 00:05:49,330
respective constants which are functions in the end as values.

76
00:05:49,340 --> 00:05:52,910
So now with that in app.js I can call db, initDb

77
00:05:52,940 --> 00:05:56,300
here and initDb needs a callback function

78
00:05:56,300 --> 00:06:07,710
as you learned, a callback function that will either give me an error or the database because here, I want

79
00:06:07,710 --> 00:06:14,840
to also call the callback with null and then the database, like this. And now in

80
00:06:14,890 --> 00:06:23,070
app.js, I know that if I'm in here, I can check if the error exists and if it does, I'll simply console log

81
00:06:23,070 --> 00:06:30,000
the error but else if I got no error, then I can call app listen which starts the nodejs server. So

82
00:06:30,000 --> 00:06:35,020
the nodejs server in this setup here here will start when the connection is established.

83
00:06:35,020 --> 00:06:41,220
Now you can always tweak this but this is a basic setup that ensures that the database is or that our

84
00:06:41,670 --> 00:06:48,370
app here connects to the database at application start up before it starts listening to incoming requests 

85
00:06:48,540 --> 00:06:52,740
and then this simply will keep on running. Now in

86
00:06:52,750 --> 00:06:53,890
products.js,

87
00:06:54,000 --> 00:06:57,300
we also don't need the mongo client anymore,

88
00:06:57,300 --> 00:07:00,400
we need mongodb though for the decimal import

89
00:07:00,630 --> 00:07:04,390
but I can now add my own import db by requiring

90
00:07:04,500 --> 00:07:09,190
and now we go up one level with two dots and then we point at db, like this,

91
00:07:09,220 --> 00:07:17,130
so in our db.js file and then in the places where we work with the database, we simply replace this entire

92
00:07:17,130 --> 00:07:19,790
part where we connect and so on

93
00:07:20,660 --> 00:07:26,890
with a call to db, getDb and that returns us the connected database and

94
00:07:26,930 --> 00:07:33,140
therefore this closing pair of brackets can be removed. And now we just interact with the database here

95
00:07:33,440 --> 00:07:36,750
and then the rest of the code stays as it is and in post,

96
00:07:36,750 --> 00:07:37,910
it's the same.

97
00:07:38,120 --> 00:07:47,900
We replace that code here with db, getDb and remove that redundant pair of brackets. With all these

98
00:07:47,900 --> 00:07:56,120
changes, let's quit our currently running backend server, restarting router get catch is not a function,

99
00:07:56,120 --> 00:07:57,590
let's see what's wrong here.

100
00:07:59,560 --> 00:08:02,020
Oh yeah, that catch block here,

101
00:08:02,140 --> 00:08:09,820
that is also redundant now because that was related to catching errors during the establishment of our connection,

102
00:08:09,820 --> 00:08:15,360
we don't need that anymore so let's remove that outer catch block on our get and post route

103
00:08:15,400 --> 00:08:21,670
so that we only have to catch block on forEach or the catch block on insert but not the one that was related

104
00:08:21,670 --> 00:08:23,220
to connecting

105
00:08:23,390 --> 00:08:25,260
and let's now try this again.

106
00:08:26,410 --> 00:08:28,140
This looks better,

107
00:08:28,270 --> 00:08:29,630
we get no error and

108
00:08:29,990 --> 00:08:35,440
if I now reload that front page here, now I have an error,

109
00:08:37,140 --> 00:08:40,090
client is not defined is the error I get here

110
00:08:41,440 --> 00:08:46,360
and that makes sense because I still have the code to close the connection which I don't need to do

111
00:08:46,400 --> 00:08:48,730
and I'll say some words about that in a second too,

112
00:08:48,860 --> 00:08:56,720
so make sure you remove all client close calls here in your products.js file and thereafter, restart.

113
00:08:58,340 --> 00:09:04,490
After reloading, I get a strange result because I accidentally deleted my products constant and therefore,

114
00:09:04,670 --> 00:09:10,400
I load my old products which I have up there. Now I should simply comment out my dummy products up there

115
00:09:10,490 --> 00:09:17,420
which I don't need anymore and then simply recreate my products down there as an empty array to which

116
00:09:17,420 --> 00:09:19,400
I push all the products.

117
00:09:19,400 --> 00:09:25,370
So now with that finally, if we now restart the backend server and we reload that starting page, we should

118
00:09:25,370 --> 00:09:28,600
see only that one product which we added.

119
00:09:28,610 --> 00:09:31,560
So now we have the same functionality as before,

120
00:09:31,740 --> 00:09:38,920
let's also confirm this by adding a new product and for this, I'll just use some of my dummy data,

121
00:09:39,100 --> 00:09:40,210
lovely earrings,

122
00:09:43,130 --> 00:09:47,210
price and the image url here simply

123
00:09:47,210 --> 00:09:52,280
is this url

124
00:09:52,390 --> 00:09:58,760
and then in there, let's also add a description like this.

125
00:09:58,780 --> 00:10:02,510
Now if I create that product, you see the lovely earrings exist here too.

126
00:10:02,830 --> 00:10:05,510
So now we got that all set up,

127
00:10:05,560 --> 00:10:08,990
we're now able to store data, to get data,

128
00:10:09,040 --> 00:10:13,380
now the next step is of course to also get data for a single product

129
00:10:13,420 --> 00:10:16,780
if I click on details here, which right now doesn't work

130
00:10:16,780 --> 00:10:23,350
and I also want to drop some words on reusing that connection which we're currently doing.

131
00:10:23,470 --> 00:10:27,820
I'm using one and the same connection all the time now and this is actually something which you should

132
00:10:27,820 --> 00:10:34,480
do because you'll use a concept called connection pooling which is provided by the mongodb driver

133
00:10:34,480 --> 00:10:36,100
here by default.

134
00:10:36,100 --> 00:10:41,100
That means it actually established a couple of connections or at least it's ready to quickly establish

135
00:10:41,110 --> 00:10:46,480
them and therefore, you can handle multiple incoming requests to your node restAPI

136
00:10:46,490 --> 00:10:53,430
simultanenuously because you can only send one request per connection to mongodb normally

137
00:10:53,650 --> 00:10:59,110
but since you have a connection pool here of multiple available connections, even if you have multiple

138
00:10:59,110 --> 00:11:04,530
incoming connections to nodejs, you can forward them to mongodb

139
00:11:04,600 --> 00:11:06,470
thanks to this connection pooling.

140
00:11:06,490 --> 00:11:12,970
So this is also an advantage of this approach where we reuse one client because here, we actually have

141
00:11:13,090 --> 00:11:14,510
a shared connection pool then.

142
00:11:14,520 --> 00:11:19,990
Now to fully reuse that though, we should not call db here,

143
00:11:20,200 --> 00:11:25,590
so db should just be the client instead and therefore in products.js

144
00:11:25,590 --> 00:11:30,730
when you call getDb, we have to call db ourselves.

145
00:11:30,730 --> 00:11:36,400
So this is one tiny change you should make to be sure you can reuse your connections but with that out

146
00:11:36,400 --> 00:11:42,960
of the way and the backend server restarted one more time, everything should still work right.

147
00:11:43,070 --> 00:11:45,560
So now let's work on getting a single product.