1 00:00:03,680 --> 00:00:06,035 In the previous lesson, 2 00:00:06,035 --> 00:00:08,550 we learned about the MongoDB driver. 3 00:00:08,550 --> 00:00:14,250 That enables our node application to communicate with a MongoDB server, 4 00:00:14,250 --> 00:00:19,660 and also store and retrieve documents from the MongoDB server. 5 00:00:19,660 --> 00:00:23,310 We also saw that the MongoDB driver provides us with 6 00:00:23,310 --> 00:00:28,770 many methods that enable us to create collections within a database, 7 00:00:28,770 --> 00:00:30,925 add documents to the collections, 8 00:00:30,925 --> 00:00:35,695 and then perform various operations on the documents within a collection. 9 00:00:35,695 --> 00:00:41,060 Now, when the documents are stored in the database, 10 00:00:41,060 --> 00:00:46,330 the MongoDB driver itself imposes no structure on the documents. 11 00:00:46,330 --> 00:00:52,640 If we need to have specific structure for the documents and enforce that structure, 12 00:00:52,640 --> 00:00:58,505 then we need to make use of the Mongoose node module which enables us to define 13 00:00:58,505 --> 00:01:05,015 a schema and a structure for our documents that are stored in our MongoDB database, 14 00:01:05,015 --> 00:01:08,275 and strictly enforces the structure. 15 00:01:08,275 --> 00:01:16,035 Let's look at more details in this lecture and the exercises that follow this lecture. 16 00:01:16,035 --> 00:01:18,540 As we have already learned, 17 00:01:18,540 --> 00:01:25,035 MongoDB stores data in collections in a database. 18 00:01:25,035 --> 00:01:28,695 These collections consists of a collection of documents. 19 00:01:28,695 --> 00:01:30,750 The documents themselves stored in 20 00:01:30,750 --> 00:01:35,405 a MongoDB database have no specific structure imposed on the document. 21 00:01:35,405 --> 00:01:38,570 Any document can be stored in any collection. 22 00:01:38,570 --> 00:01:46,370 MongoDB relies on the developer to enforce the structure on the documents, 23 00:01:46,370 --> 00:01:52,295 and gives the complete responsibility to the developer to make sure that documents 24 00:01:52,295 --> 00:01:58,670 of the correct structure are added and maintained in the various collections. 25 00:01:58,670 --> 00:02:01,960 Now, it is very easy to violate this. 26 00:02:01,960 --> 00:02:06,260 So for example, even though you might start out with the assumption 27 00:02:06,260 --> 00:02:11,030 that a particular connection will have documents of a certain structure, 28 00:02:11,030 --> 00:02:17,045 you can easily insert documents that don't necessarily comply with the structure. 29 00:02:17,045 --> 00:02:21,170 If you are very particular that the structure of the documents in 30 00:02:21,170 --> 00:02:25,550 a collection always have a specified structure, 31 00:02:25,550 --> 00:02:28,550 and always will have the specific set of fields, 32 00:02:28,550 --> 00:02:32,540 then the MongoDB itself doesn't impose that neither 33 00:02:32,540 --> 00:02:36,630 does the node MongoDB driver that we have seen in the previous lesson. 34 00:02:36,630 --> 00:02:40,565 This is where we will need a more formal way of imposing 35 00:02:40,565 --> 00:02:46,385 structure on the documents that are stored in a collection in a MongoDB database. 36 00:02:46,385 --> 00:02:52,390 This is where the Mongoose node module comes to our help. 37 00:02:52,390 --> 00:02:56,405 The Mongoose node module imposes 38 00:02:56,405 --> 00:03:01,875 a standardized structure for the documents that are stored in a particular collection. 39 00:03:01,875 --> 00:03:07,175 So, that is why we often hear people referring to this as the Mongoose ODM. 40 00:03:07,175 --> 00:03:10,950 The ODM itself is interpreted by some people to mean 41 00:03:10,950 --> 00:03:16,995 Object Data Model or sometimes referred to as Object Document Mapping, 42 00:03:16,995 --> 00:03:22,125 or some people refer to it as ORM or Object Relational Mapping. 43 00:03:22,125 --> 00:03:27,755 Now, when we talk about relational that applies a lot more to relational databases, 44 00:03:27,755 --> 00:03:33,380 but then with SQL databases we needed explicitly the object to 45 00:03:33,380 --> 00:03:41,850 relational mapping to be put in between the database and our application itself. 46 00:03:41,850 --> 00:03:45,245 Because within the application we would be looking at 47 00:03:45,245 --> 00:03:50,245 objects but their storage in an SQL database will be in the form of records, 48 00:03:50,245 --> 00:03:52,585 and so you need an explicit mapping. 49 00:03:52,585 --> 00:03:54,870 As we saw with the NoSQL database, 50 00:03:54,870 --> 00:03:56,685 this was not explicitly required. 51 00:03:56,685 --> 00:04:03,710 But if you need to impose structure on your documents that are stored in a collection 52 00:04:03,710 --> 00:04:10,790 then the use of Mongoose to impose this structure is very, very useful. 53 00:04:10,790 --> 00:04:13,880 The way Mongoose goes around 54 00:04:13,880 --> 00:04:18,275 imposing structure on the documents is through the use of schema. 55 00:04:18,275 --> 00:04:21,995 Schema, defines the structure of their documents. 56 00:04:21,995 --> 00:04:24,800 Let's talk about that in a bit more detail. 57 00:04:24,800 --> 00:04:27,580 So, what exactly is mongoose schema, 58 00:04:27,580 --> 00:04:29,700 and what does it bring to the table? 59 00:04:29,700 --> 00:04:34,700 Mongoose schema, implies a structure on 60 00:04:34,700 --> 00:04:39,735 the data that is stored in a document in your database. 61 00:04:39,735 --> 00:04:42,770 So, it defines all the fields of your document, 62 00:04:42,770 --> 00:04:45,349 and also specifies the types of the fields, 63 00:04:45,349 --> 00:04:47,345 and also can provide us with 64 00:04:47,345 --> 00:04:51,965 additional features that can enable validation on these fields. 65 00:04:51,965 --> 00:04:59,425 So, for example, the various schema types that are supported in Mongoose include: String, 66 00:04:59,425 --> 00:05:03,195 Number, Date, Buffer, Boolean, 67 00:05:03,195 --> 00:05:06,295 Mixed, object ID, and Array. 68 00:05:06,295 --> 00:05:09,070 In particular we will look at string number, 69 00:05:09,070 --> 00:05:14,405 and a date, and Boolean in the exercise that follows. 70 00:05:14,405 --> 00:05:18,075 We will look at some of the other ones in later exercises. 71 00:05:18,075 --> 00:05:22,125 In particular, notice the use of the array schema type. 72 00:05:22,125 --> 00:05:25,570 So, an array schema type would allow you to 73 00:05:25,570 --> 00:05:31,640 create an array of sub-documents inside the document. 74 00:05:31,640 --> 00:05:33,740 I'll talk about that in a short while. 75 00:05:33,740 --> 00:05:36,940 Once you define a schema, 76 00:05:36,960 --> 00:05:42,160 the schema is then used in Mongoose to create a model function, 77 00:05:42,160 --> 00:05:49,830 and that is what enables you to define the structure for your documents in the database. 78 00:05:49,830 --> 00:05:53,225 Schemas themselves can have nesting. 79 00:05:53,225 --> 00:05:58,490 So, which means that you can have sub-document that are enclosed inside a document. 80 00:05:58,490 --> 00:06:01,519 The sub-documents typically are accommodated 81 00:06:01,519 --> 00:06:04,890 either through specifying an additional schema, 82 00:06:04,890 --> 00:06:11,870 and then defining one of the fields of the schema to be off the type of the other schema. 83 00:06:11,870 --> 00:06:15,215 Or you can even go with an array of 84 00:06:15,215 --> 00:06:20,000 another schema type within a second schema that you define. 85 00:06:20,000 --> 00:06:24,930 Let's look at an example to clarify some of these in more detail. 86 00:06:24,930 --> 00:06:32,010 This example will be from the exercise that you will do right after this lecture. 87 00:06:32,010 --> 00:06:37,705 Before I can talk about schemas and models in Mongoose, 88 00:06:37,705 --> 00:06:41,310 let's understand why we would need that. 89 00:06:41,310 --> 00:06:43,975 If you have taken the previous angular, 90 00:06:43,975 --> 00:06:46,760 or the ionic, or the native script course, 91 00:06:46,760 --> 00:06:49,445 you have seen that we represent 92 00:06:49,445 --> 00:06:55,565 various data that we use in our applications in the form of JSON strings. 93 00:06:55,565 --> 00:07:02,050 So, in our application we define a collection called as dishes. 94 00:07:02,050 --> 00:07:03,770 In a dish collection, 95 00:07:03,770 --> 00:07:09,700 each dish will contain a certain set of properties defined in the form of JSON string, 96 00:07:09,700 --> 00:07:11,665 as you see in this example here. 97 00:07:11,665 --> 00:07:15,830 So, the dishes is an array of dish type, 98 00:07:15,830 --> 00:07:18,605 and each dish itself will contain a name, 99 00:07:18,605 --> 00:07:20,290 an image, a category, 100 00:07:20,290 --> 00:07:22,015 a label, and so on. 101 00:07:22,015 --> 00:07:26,360 Also, inside the dish document itself, 102 00:07:26,360 --> 00:07:32,830 you would have comments which are stored as an array of again,- 103 00:07:32,830 --> 00:07:38,240 JSON documents which contain specific fields step. 104 00:07:38,240 --> 00:07:39,750 So, each comment, for example, 105 00:07:39,750 --> 00:07:45,685 contains a rating comment author and a date field as you see in this example here. 106 00:07:45,685 --> 00:07:49,215 So, you see that there is a clear structure to 107 00:07:49,215 --> 00:07:55,230 each document that defines a dish that is stored in our database. 108 00:07:55,230 --> 00:08:02,545 Multiple dishes obviously will be stored in the form of a collection in our database, 109 00:08:02,545 --> 00:08:06,655 and could be grouped together and sent over as an array of 110 00:08:06,655 --> 00:08:11,165 dishes to our client application to be made use of. 111 00:08:11,165 --> 00:08:14,890 Now that we have understood how this is defined, now, 112 00:08:14,890 --> 00:08:22,000 how does this relate to the Mongoose schema and the model that we define in Mongoose? 113 00:08:22,000 --> 00:08:27,460 Now, note the structure of a typical dish document here. 114 00:08:27,460 --> 00:08:34,095 So, this could be easily mapped into a MongoDB document in a collection, 115 00:08:34,095 --> 00:08:37,375 perhaps named the dishes collection. 116 00:08:37,375 --> 00:08:42,605 So, we see that there is a clear structure to the document itself. 117 00:08:42,605 --> 00:08:50,320 Now, how do we mirror this in a schema in our Mongoose application? 118 00:08:50,320 --> 00:08:54,095 As you will learn in the exercise, 119 00:08:54,095 --> 00:08:57,900 we will see that we would define schemas in Mongoose. 120 00:08:57,900 --> 00:09:03,085 So the schema is defined as a Mongoose schema here. 121 00:09:03,085 --> 00:09:08,055 As an example, a commentSchema is shown here. 122 00:09:08,055 --> 00:09:09,925 The commentSchema, as you can see, 123 00:09:09,925 --> 00:09:13,885 contains three different fields: the rating, comment, 124 00:09:13,885 --> 00:09:15,445 and the author field, 125 00:09:15,445 --> 00:09:18,745 and also timestamps here. 126 00:09:18,745 --> 00:09:23,560 The timestamps allow you to have two different fields in 127 00:09:23,560 --> 00:09:28,850 the document: the created at field and the updated at field, 128 00:09:28,850 --> 00:09:38,200 both of which are timestamps stored in the form of an ISO date string in the document. 129 00:09:38,200 --> 00:09:43,615 Now, the rating itself would be an integer value. 130 00:09:43,615 --> 00:09:46,400 So, in Mongoose terminology, 131 00:09:46,400 --> 00:09:48,755 it will be stored as a number, 132 00:09:48,755 --> 00:09:50,680 the type would be a number. 133 00:09:50,680 --> 00:09:53,660 You can even specify the minimum and the maximum value. 134 00:09:53,660 --> 00:09:57,190 You can also specify that this particular field is required, so, 135 00:09:57,190 --> 00:10:04,460 which means that every document of the comment type should contain a rating field. 136 00:10:04,460 --> 00:10:07,370 Similarly, you can also define a comment field, 137 00:10:07,370 --> 00:10:08,710 which is of the type string. 138 00:10:08,710 --> 00:10:13,635 So, obviously, a comment is nothing but a string which contains some information, 139 00:10:13,635 --> 00:10:16,340 and this can also be defined as a required field, 140 00:10:16,340 --> 00:10:18,805 meaning that every document should contain a comment, 141 00:10:18,805 --> 00:10:21,060 and also an author field, 142 00:10:21,060 --> 00:10:22,800 which is also of the type string. 143 00:10:22,800 --> 00:10:28,030 So, you see that by defining this schema in this format. 144 00:10:28,030 --> 00:10:32,600 As we learned in the discussion a little bit earlier, 145 00:10:32,600 --> 00:10:41,890 schema is defined by using the various types that we have in our Mongoose application. 146 00:10:41,890 --> 00:10:43,030 So, in the schema, again, 147 00:10:43,030 --> 00:10:44,900 you see three different fields here, 148 00:10:44,900 --> 00:10:47,135 rating, comment, and author here, 149 00:10:47,135 --> 00:10:50,665 and each of which has a specific type given, 150 00:10:50,665 --> 00:10:53,060 and then whether this is required or not. 151 00:10:53,060 --> 00:10:56,505 So, thereby, you are imposing a strict structure 152 00:10:56,505 --> 00:11:01,320 on the comment documents that are going to be storing in your application. 153 00:11:01,320 --> 00:11:05,255 Now that we have defined a comment schema, we can then, 154 00:11:05,255 --> 00:11:12,254 as you noticed from the example of the kind of data that we require in our application, 155 00:11:12,254 --> 00:11:15,000 we have a dish document itself. 156 00:11:15,000 --> 00:11:17,620 The dish document contains various fields. 157 00:11:17,620 --> 00:11:19,050 Here, in the exercise, 158 00:11:19,050 --> 00:11:23,355 we will first introduce just two fields into the dish document, 159 00:11:23,355 --> 00:11:25,370 the name, and the description. 160 00:11:25,370 --> 00:11:27,010 In the next lesson, 161 00:11:27,010 --> 00:11:32,330 we will introduce the remaining fields for the dishSchema. 162 00:11:32,330 --> 00:11:33,680 Now, so the name, 163 00:11:33,680 --> 00:11:35,440 as in this case, 164 00:11:35,440 --> 00:11:36,765 is of the type string. 165 00:11:36,765 --> 00:11:39,450 We can also specify that this is a required field, 166 00:11:39,450 --> 00:11:43,360 meaning that every document should contain the name field. 167 00:11:43,360 --> 00:11:46,385 We can also specify that the name field is unique, 168 00:11:46,385 --> 00:11:53,215 meaning that no two documents can have exactly the same name value in the document. 169 00:11:53,215 --> 00:11:55,980 So, that ensures that each document will have 170 00:11:55,980 --> 00:12:01,300 a unique name field in it and a description field, 171 00:12:01,300 --> 00:12:03,115 which is again of the type string, 172 00:12:03,115 --> 00:12:06,460 but also specified as required. 173 00:12:06,460 --> 00:12:10,010 Now, as we saw in the example, 174 00:12:10,010 --> 00:12:15,750 a dish document contains multiple comments enclosed inside the document. 175 00:12:15,750 --> 00:12:20,920 Now, in Mongoose, this is supported through the use of sub-documents. 176 00:12:20,920 --> 00:12:24,230 So, if you define a schema earlier, 177 00:12:24,230 --> 00:12:27,345 so for example, we have already defined a commentSchema here, 178 00:12:27,345 --> 00:12:33,370 you can also define a field into another schema that you define and 179 00:12:33,370 --> 00:12:36,240 then specify that that field will be of 180 00:12:36,240 --> 00:12:39,520 the type of the previous schema that you have defined. 181 00:12:39,520 --> 00:12:40,960 So, in this case, 182 00:12:40,960 --> 00:12:44,360 the comments field, I am defining it as an array, 183 00:12:44,360 --> 00:12:51,545 so you see the use of an array type in your schema that you're defining here, 184 00:12:51,545 --> 00:12:55,110 and then array of the commentSchema type. 185 00:12:55,110 --> 00:13:00,725 So, this is an array of comments that will be included in each dish document. 186 00:13:00,725 --> 00:13:02,590 So, thereby, you can have 187 00:13:02,590 --> 00:13:11,640 more than one comment sub-document enclosed inside a dish document. 188 00:13:11,640 --> 00:13:16,080 So, defining the structure like this enables us to support 189 00:13:16,080 --> 00:13:20,950 the corresponding JSON string structure that we have defined 190 00:13:20,950 --> 00:13:26,470 for a dish document or that we have seen in the example earlier. 191 00:13:26,470 --> 00:13:30,145 Now, once we define the schema, 192 00:13:30,145 --> 00:13:33,695 to make use of this in our application, 193 00:13:33,695 --> 00:13:38,600 we need to create a model from that schema that we have just defined. 194 00:13:38,600 --> 00:13:40,640 So, within our application, 195 00:13:40,640 --> 00:13:45,320 we will define a Mongoose model and specify that the model 196 00:13:45,320 --> 00:13:51,085 is off the type dishSchema in this example. 197 00:13:51,085 --> 00:13:54,830 Not only that, you will also give a name to the model here. 198 00:13:54,830 --> 00:13:57,100 So, when you give a name to the model here, 199 00:13:57,100 --> 00:14:00,000 we are specifying the name as dish. 200 00:14:00,000 --> 00:14:03,860 Now, when you use this dish model in 201 00:14:03,860 --> 00:14:07,870 our node application where we are making use of Mongoose, 202 00:14:07,870 --> 00:14:15,280 then this will be transformed and mapped into a collection in my MongoDB database. 203 00:14:15,280 --> 00:14:18,885 The collection itself will be named as dishes. 204 00:14:18,885 --> 00:14:23,355 So, Mongoose automatically knows that when you specify a name here, 205 00:14:23,355 --> 00:14:27,990 it'll automatically construct the plural 206 00:14:27,990 --> 00:14:31,635 of that name and then give the collection the name, 207 00:14:31,635 --> 00:14:37,160 which is the plural of the model name that you specify in this example here. 208 00:14:37,160 --> 00:14:39,400 So, when I say dish here, 209 00:14:39,400 --> 00:14:42,620 then Mongoose automatically will map this into 210 00:14:42,620 --> 00:14:46,365 the dishes collection in the MongoDB database. 211 00:14:46,365 --> 00:14:53,385 How does it know how to convert this singular name to a plural? 212 00:14:53,385 --> 00:14:56,750 Mongoose automatically has a built-in mechanism that 213 00:14:56,750 --> 00:15:01,795 enables it to construct the plurals of standard English words. 214 00:15:01,795 --> 00:15:02,965 So, if you say dish, 215 00:15:02,965 --> 00:15:04,170 it will construct dishes. 216 00:15:04,170 --> 00:15:08,880 If you say leader, it will construct the plural of it as leaders, and so on. 217 00:15:08,880 --> 00:15:13,250 So, this is already built into the Mongoose node module. 218 00:15:13,250 --> 00:15:17,585 So, that is why when I specify this as a dish model type, 219 00:15:17,585 --> 00:15:24,050 then Mongoose will construct the dishes collection in my MongoDB database, 220 00:15:24,050 --> 00:15:27,155 and then that dishes collection will store 221 00:15:27,155 --> 00:15:33,050 the various documents of the dish type in there. 222 00:15:33,050 --> 00:15:35,780 Once we have created that, typically, 223 00:15:35,780 --> 00:15:38,150 when we declare models in our application, 224 00:15:38,150 --> 00:15:43,780 we would store them in a sub-folder named models, just for convenience. 225 00:15:43,780 --> 00:15:44,900 You don't need to do that, 226 00:15:44,900 --> 00:15:47,320 but just to organize your application, 227 00:15:47,320 --> 00:15:50,635 we would normally store that in a folder named models. 228 00:15:50,635 --> 00:15:55,010 Then the schema and the model would be 229 00:15:55,010 --> 00:15:59,470 defined in a file like this as you see in the example here, 230 00:15:59,470 --> 00:16:05,230 this called dishes.js, and then this would be exported because this is a node module. 231 00:16:05,230 --> 00:16:10,970 This'll be exported from this file so that it can be included into the node application, 232 00:16:10,970 --> 00:16:13,100 where we are going to make use of 233 00:16:13,100 --> 00:16:16,620 this schema and the model that we have just defined here. 234 00:16:16,620 --> 00:16:20,540 With this quick understanding of schema and model and 235 00:16:20,540 --> 00:16:26,370 its use in defining the structure for a document that we store in a MongoDB, 236 00:16:26,370 --> 00:16:33,510 let's go back and understand a little more about what Mongoose provides for us. 237 00:16:33,510 --> 00:16:39,965 In addition, Mongoose enables us to establish the connection with the MongoDB server. 238 00:16:39,965 --> 00:16:43,070 Mongoose internally make use of 239 00:16:43,070 --> 00:16:46,495 the MongoDB driver that we had used in the previous exercise. 240 00:16:46,495 --> 00:16:49,745 So, Mongoose depends upon the MongoDB driver, so, 241 00:16:49,745 --> 00:16:53,824 which means that from your Mongoose-based node application, 242 00:16:53,824 --> 00:16:56,960 you can use all the methods that are already 243 00:16:56,960 --> 00:17:01,040 available from the MongoDB driver also if you choose to, 244 00:17:01,040 --> 00:17:05,390 but Mongoose itself has its own collection of methods that we 245 00:17:05,390 --> 00:17:09,940 can make use of to interact with the MongoDB database, 246 00:17:09,940 --> 00:17:13,645 as we will see in the exercise that follows. 247 00:17:13,645 --> 00:17:19,040 Let me briefly show you how we would establish a connection to the database, 248 00:17:19,040 --> 00:17:21,590 and you will do this in the exercise that follows. 249 00:17:21,590 --> 00:17:25,280 So, just like we declared the URL in case 250 00:17:25,280 --> 00:17:29,160 of the MongoDB node application in the earlier lesson, 251 00:17:29,160 --> 00:17:32,630 we will still declare the URL for our application. 252 00:17:32,630 --> 00:17:36,965 Then we will use the Mongoose connect method 253 00:17:36,965 --> 00:17:40,180 and supply the URL for the Mongoose connect method, 254 00:17:40,180 --> 00:17:44,000 and this will establish the connection to the database. 255 00:17:44,000 --> 00:17:48,590 With this quick understanding of Mongoose and what role Mongoose 256 00:17:48,590 --> 00:17:53,485 plays in supporting structured insertion, 257 00:17:53,485 --> 00:17:58,985 storage, and retrieval of documents from our MongoDB, 258 00:17:58,985 --> 00:18:02,180 let's move on to the exercise where we will 259 00:18:02,180 --> 00:18:07,920 get some hands-on experience using the Mongoose module.