1 00:00:07,360 --> 00:00:08,620 In this video. 2 00:00:08,620 --> 00:00:18,630 Let's talk about another way of relating data, and that is by referencing when we say by referencing, 3 00:00:18,640 --> 00:00:20,020 what does it mean? 4 00:00:20,260 --> 00:00:30,400 It simply means that we are going to save the ID of a document into a field and we use a special type 5 00:00:30,400 --> 00:00:39,550 called Mongoose dot schema, dot types, dot object ID, meaning that we are going to save the ID of 6 00:00:39,550 --> 00:00:46,720 a document, but for embedded we save the entire object into a field. 7 00:00:46,750 --> 00:00:49,660 As we see in this slide. 8 00:00:49,750 --> 00:00:58,190 So here comes the question when do we need to use the embedded and when do we need to use the reference? 9 00:00:58,210 --> 00:01:01,750 Here is the answer we use embedded. 10 00:01:01,780 --> 00:01:09,670 If you know that in future that particular field will not grow too much, for example, a product and 11 00:01:09,670 --> 00:01:10,450 a review. 12 00:01:10,450 --> 00:01:16,930 In that way we can use the embedded way, but a post and a command. 13 00:01:16,930 --> 00:01:24,720 We need to use the reference because a post can have millions comment as compared to a review. 14 00:01:24,730 --> 00:01:32,050 So the best way to go is to use the referencing, and the referencing is the most recommended way of 15 00:01:32,050 --> 00:01:33,820 relating documents. 16 00:01:33,820 --> 00:01:36,190 So let's see them in action. 17 00:01:36,280 --> 00:01:38,800 So back to Visual Studio code. 18 00:01:38,800 --> 00:01:44,080 I have cleaned up the previous code and now it's back to default. 19 00:01:44,230 --> 00:01:48,370 In your case, we can make a copy for future reference. 20 00:01:48,370 --> 00:01:53,410 So for the post schema, this what we have the title and the contents. 21 00:01:53,440 --> 00:01:55,030 Likewise the user. 22 00:01:55,030 --> 00:02:00,000 We have the full name and then the country and inside the post. 23 00:02:00,010 --> 00:02:00,640 Right. 24 00:02:00,790 --> 00:02:05,870 You can see that this is a normal way of saving the command into MongoDB. 25 00:02:05,920 --> 00:02:10,570 Likewise, the function to there is nothing new here. 26 00:02:10,660 --> 00:02:13,120 Likewise the user too. 27 00:02:13,150 --> 00:02:20,350 You can see that we are saving a user document into DB and here we find the user. 28 00:02:20,350 --> 00:02:24,160 So these two modules are not related. 29 00:02:24,160 --> 00:02:28,230 So let's see how we can relate these two documents. 30 00:02:28,240 --> 00:02:29,770 Here is a clue. 31 00:02:29,980 --> 00:02:36,700 We are creating a blog application, meaning that a user can create many posts. 32 00:02:36,700 --> 00:02:39,370 So let's see how we are going to model that. 33 00:02:39,370 --> 00:02:42,820 So let's get back to the user model. 34 00:02:42,850 --> 00:02:50,470 So for this we are going to save the post, the user is going to create as part of it. 35 00:02:50,470 --> 00:02:52,690 Field So here we go. 36 00:02:52,720 --> 00:02:57,220 We bring in the post and here is the clue. 37 00:02:57,310 --> 00:03:02,170 This post must be an array, but what type of array? 38 00:03:02,170 --> 00:03:07,510 So let me show you here we bring in the array and then the object. 39 00:03:07,510 --> 00:03:21,400 And for this, the type is going to be as mongoose, dot schema, dot types, dot object ID and the 40 00:03:21,400 --> 00:03:24,970 next field is going to be the reference. 41 00:03:24,970 --> 00:03:27,610 So which model are we referencing? 42 00:03:27,610 --> 00:03:30,760 We are referencing the post model. 43 00:03:30,790 --> 00:03:37,600 Make sure that you type the exact name as the name of the model as we see here. 44 00:03:37,600 --> 00:03:41,140 So now we are done with the user. 45 00:03:41,530 --> 00:03:48,280 And also if you find a post, we want to know what user created that post. 46 00:03:48,340 --> 00:03:53,770 In that way we need to go to post and then add the author field. 47 00:03:53,770 --> 00:03:55,600 So here we go. 48 00:03:55,630 --> 00:03:59,560 We will add the author or the user for this. 49 00:03:59,560 --> 00:04:02,680 Let's make it as order for this. 50 00:04:02,680 --> 00:04:09,520 We can use the entire user because a post might have only one author. 51 00:04:09,640 --> 00:04:14,740 But the ideal way to go is to use the object ID. 52 00:04:14,860 --> 00:04:23,590 So the type here is going to be as we did for post mongoose dot schema, dot type dot object. 53 00:04:23,590 --> 00:04:26,660 ID take note about the common casing. 54 00:04:26,740 --> 00:04:33,310 And we also want to reference which model that is a user model and that is it. 55 00:04:33,310 --> 00:04:35,230 We are done with the relationship. 56 00:04:35,230 --> 00:04:39,520 So now let's get back to the root and create a post. 57 00:04:39,670 --> 00:04:48,850 So inside the client, let's go ahead and then register a user and now I'm going to use Joe and then 58 00:04:48,850 --> 00:04:57,550 country Ghana, I'll hit send and now you can see that we have a property called Post which is an array 59 00:04:57,550 --> 00:05:03,470 and by default it is empty because this user hasn't created a new post yet. 60 00:05:03,580 --> 00:05:06,520 Before we continue, let's finish up this one. 61 00:05:06,890 --> 00:05:13,910 This auto field must be a required fake, meaning that we need to look in before you can create. 62 00:05:13,910 --> 00:05:16,280 So let's add required to. 63 00:05:17,030 --> 00:05:21,110 But for a post on the user that I'm going to be optional. 64 00:05:21,140 --> 00:05:22,510 So here we go. 65 00:05:22,520 --> 00:05:25,370 So back to the post and points. 66 00:05:25,400 --> 00:05:31,100 Let's go ahead and create, but make sure that we copy the ID of the user. 67 00:05:31,130 --> 00:05:33,460 So let's go ahead and create that one. 68 00:05:33,470 --> 00:05:39,980 So back to the post route here and let's add the payload that we want to create. 69 00:05:40,010 --> 00:05:45,950 We need the title of the post and let me call this one as a HTML. 70 00:05:46,130 --> 00:05:55,550 And we need the content of the post and let's say the best posts ever. 71 00:05:55,640 --> 00:06:00,350 And when I hit send, you can see that I'm going to get some validation error. 72 00:06:00,380 --> 00:06:04,300 Simply mean that this sort of field is required. 73 00:06:04,310 --> 00:06:07,030 So let's go ahead and then do that one. 74 00:06:07,040 --> 00:06:10,500 So let's add a property called author. 75 00:06:10,520 --> 00:06:18,950 Well, if you're doing production application, we can get the author for the request object because 76 00:06:18,950 --> 00:06:20,450 we haven't done authentication. 77 00:06:20,450 --> 00:06:23,060 That's why I'm passing it manually here. 78 00:06:23,060 --> 00:06:24,470 So I'll pass that one. 79 00:06:24,470 --> 00:06:27,090 And next is our hit save. 80 00:06:27,110 --> 00:06:36,800 But before saving, well, we want to save the post this user has created into the field of this user. 81 00:06:36,800 --> 00:06:42,830 So before we save it, let's finish up the logic inside the post route. 82 00:06:42,830 --> 00:06:44,390 So here we go. 83 00:06:44,390 --> 00:06:47,410 So let's lay out the steps here. 84 00:06:47,660 --> 00:07:00,860 So step number one is we need to find the user by ID and remember we are passing the user as author 85 00:07:01,010 --> 00:07:03,940 so we can go ahead and then find the user. 86 00:07:03,950 --> 00:07:05,390 So here we go. 87 00:07:05,390 --> 00:07:07,070 Find the. 88 00:07:08,400 --> 00:07:18,180 User and as simple as cons user found is equal to our weight. 89 00:07:18,180 --> 00:07:30,530 And then the user model dot find by ID and I want to find buy rec dot body dot author where you can 90 00:07:30,660 --> 00:07:33,060 structure the body object. 91 00:07:33,270 --> 00:07:42,690 So here we can check that if there is no user found, then we can go ahead and then return and send 92 00:07:42,690 --> 00:07:51,630 some Jason data to the user by saying that message and user not found. 93 00:07:51,960 --> 00:07:59,930 Otherwise we can go ahead and then push the seatpost into the field of the user post. 94 00:07:59,940 --> 00:08:12,870 So next step is step number two is save the created post into the user's post failed. 95 00:08:13,320 --> 00:08:14,760 So here we go. 96 00:08:14,790 --> 00:08:19,600 Now on user found, we have a property called Post. 97 00:08:19,620 --> 00:08:20,670 Did you see that? 98 00:08:20,670 --> 00:08:26,760 And one that we are going to push the post ID for this one. 99 00:08:26,760 --> 00:08:29,670 We are going to save the entire post. 100 00:08:29,880 --> 00:08:33,870 It can happen that a post might have less say more properties here. 101 00:08:33,960 --> 00:08:37,980 But for this case we are just going to save the ID only. 102 00:08:38,100 --> 00:08:42,299 So for this we can use the entire object. 103 00:08:42,299 --> 00:08:51,870 And behind this scene Mongoose is going to use the ID only because we specify as an object ID or we 104 00:08:51,870 --> 00:08:56,220 can specify also as the underscore ID. 105 00:08:56,400 --> 00:09:04,100 Then the next step is that because we have made changes to the user documents we need to receive. 106 00:09:04,880 --> 00:09:05,490 Great. 107 00:09:05,490 --> 00:09:06,780 So here we go. 108 00:09:06,810 --> 00:09:07,680 And wait. 109 00:09:07,680 --> 00:09:13,420 And then user found dot C and that is it. 110 00:09:13,440 --> 00:09:17,880 So with this one, I can go ahead and then make the request. 111 00:09:17,880 --> 00:09:19,130 So check it out. 112 00:09:19,140 --> 00:09:26,180 When I hit st this time around I get some error because I'm not passing in the user. 113 00:09:26,190 --> 00:09:34,560 So here I'm going to be as the author and going to be as rec dot body dot author. 114 00:09:34,590 --> 00:09:36,780 So now moment of truth. 115 00:09:36,780 --> 00:09:38,280 Let's hit st. 116 00:09:38,280 --> 00:09:40,560 I guess something now is loading. 117 00:09:41,040 --> 00:09:44,600 Let's wait for and here we go. 118 00:09:44,610 --> 00:09:50,750 You can see that now we are waiting this post by a user. 119 00:09:50,760 --> 00:09:55,500 So if you go ahead and then fetch all users. 120 00:09:55,530 --> 00:09:58,200 Now let's click on fetch all users here. 121 00:09:58,230 --> 00:10:08,490 And this time around we have a field of post and we have the ID of the post, but not the entire document. 122 00:10:08,520 --> 00:10:10,770 How awesome it is. 123 00:10:10,920 --> 00:10:17,220 Again, let me prove to you before I end up this here, and like I said, that we can save the entire 124 00:10:17,220 --> 00:10:22,170 object and behind the scene, Mongoose is going to take the ID only. 125 00:10:22,290 --> 00:10:23,250 Let's save it. 126 00:10:23,250 --> 00:10:26,500 And now let's go ahead and create a new post here. 127 00:10:26,670 --> 00:10:28,200 This time around, they change. 128 00:10:28,200 --> 00:10:34,800 This one to note, J is now the same author Let's hit send. 129 00:10:35,590 --> 00:10:40,440 And I got the response if I'll fetch or uses. 130 00:10:40,450 --> 00:10:46,720 You can see that mongoose is smart by taking the ID from the entire object. 131 00:10:46,750 --> 00:10:48,090 How awesome it is. 132 00:10:48,100 --> 00:10:50,670 So here comes the another question. 133 00:10:50,680 --> 00:10:53,590 How will I know the real post here? 134 00:10:53,620 --> 00:10:55,350 Likewise the post. 135 00:10:55,360 --> 00:11:00,960 How will I know the actual user than using the ID as we did before? 136 00:11:00,970 --> 00:11:03,900 We are going to use the populate method. 137 00:11:03,910 --> 00:11:12,700 So now back to the user user route here on fetching, we are going to populate the posts. 138 00:11:12,700 --> 00:11:22,270 So here you pass in the post, make sure that this value or this variable is on the user model because 139 00:11:22,270 --> 00:11:24,910 we have it already as post. 140 00:11:24,910 --> 00:11:28,960 So now let's save it and let's fetch our user. 141 00:11:28,960 --> 00:11:35,890 And this time around we go back the to our post than the ID. 142 00:11:35,920 --> 00:11:41,050 So upon requesting that's where we are going to go to populate it. 143 00:11:41,050 --> 00:11:43,240 How awesome this one is. 144 00:11:43,450 --> 00:11:49,060 Likewise, the post may be asking How will I know which user created this post? 145 00:11:49,060 --> 00:11:57,040 So as we did for user, we are going to populate that one and we use what is called author on the post 146 00:11:57,040 --> 00:11:57,460 field. 147 00:11:57,460 --> 00:12:01,000 Let me show you before I make the request, which is this. 148 00:12:01,000 --> 00:12:07,170 So now let's save this one and now let's go ahead and then fetch all posts. 149 00:12:07,180 --> 00:12:12,730 Now this is the end point to fetch or post here and let's hit send. 150 00:12:12,730 --> 00:12:15,790 And now we have two posts. 151 00:12:15,790 --> 00:12:26,290 One is the HTML with the author as this and then the post number two as node and then the author as 152 00:12:26,290 --> 00:12:26,920 this. 153 00:12:26,920 --> 00:12:30,580 And you can see that this post caused the IDs. 154 00:12:30,580 --> 00:12:36,490 So how can we make public to this one unless we do what is called nesting population? 155 00:12:36,700 --> 00:12:43,660 So back to the post route here to be able to use the populate, you are going to change the way we are 156 00:12:43,660 --> 00:12:44,410 doing this. 157 00:12:44,410 --> 00:12:52,540 Well, for this one too, we can achieve the same thing by using object and providing a path and the 158 00:12:52,540 --> 00:12:56,230 value must be a property on the post. 159 00:12:56,230 --> 00:12:57,700 So going to be the same thing. 160 00:12:57,700 --> 00:13:04,780 So let's save it this time around you're going to get and we got the same or not we need to find the 161 00:13:04,780 --> 00:13:12,490 post this one so let's thank and you can see that we have the same result but for this one we have more 162 00:13:12,490 --> 00:13:17,530 control how we can populate what is called nesting document. 163 00:13:17,530 --> 00:13:19,810 So this is the post route. 164 00:13:19,900 --> 00:13:29,380 So here we bring in populate again and as an object and then we specify the path. 165 00:13:29,380 --> 00:13:37,720 And the path this time around is called post and we can go ahead and also specify the model and this 166 00:13:37,720 --> 00:13:39,850 one is post model. 167 00:13:39,940 --> 00:13:46,750 So save it and now let's make the requests and here we go. 168 00:13:46,750 --> 00:13:56,440 And this time around we go back the actual author and the post to we go back the actual post. 169 00:13:56,620 --> 00:14:03,280 So this is what we call referencing and this is the most recommended way. 170 00:14:03,280 --> 00:14:06,730 And I advise you to stick to this method. 171 00:14:06,820 --> 00:14:07,360 All right. 172 00:14:07,360 --> 00:14:14,350 In this video, let me show you one cool thing about Mongoose, and that is virtual properties.