1 00:00:01,100 --> 00:00:02,860 ‫Just like Express, 2 00:00:02,860 --> 00:00:06,080 ‫Mongoose also has the concept of middleware. 3 00:00:06,080 --> 00:00:08,270 ‫And so let's now learn about the first type 4 00:00:08,270 --> 00:00:11,163 ‫of middleware, which is document middleware. 5 00:00:12,830 --> 00:00:15,330 ‫Now, just like with Express, we can use 6 00:00:15,330 --> 00:00:17,860 ‫Mongoose middleware to make something happen 7 00:00:17,860 --> 00:00:19,430 ‫between two events. 8 00:00:19,430 --> 00:00:22,740 ‫For example, each time a new document is saved 9 00:00:22,740 --> 00:00:25,740 ‫to the database, we can run a function 10 00:00:25,740 --> 00:00:29,450 ‫between the save command is issued and the actual saving 11 00:00:29,450 --> 00:00:33,480 ‫of the document, or also after the actual saving. 12 00:00:33,480 --> 00:00:35,820 ‫And that's the reason why Mongoose middleware 13 00:00:35,820 --> 00:00:38,590 ‫is also called pre and post hooks. 14 00:00:38,590 --> 00:00:41,140 ‫So again, because we can define functions 15 00:00:41,140 --> 00:00:44,710 ‫to run before or after a certain event, 16 00:00:44,710 --> 00:00:47,100 ‫like saving a document to the database. 17 00:00:47,100 --> 00:00:52,100 ‫So middleware is an absolutely fundamental concept 18 00:00:52,100 --> 00:00:55,180 ‫in Mongoose, so just like in Express. 19 00:00:55,180 --> 00:00:57,190 ‫And there are tons of possibilities 20 00:00:57,190 --> 00:00:59,780 ‫and use cases for middleware, and we're gonna be 21 00:00:59,780 --> 00:01:02,540 ‫using middleware all the time in this project. 22 00:01:02,540 --> 00:01:06,050 ‫So there are four types of middleware in Mongoose: 23 00:01:06,050 --> 00:01:10,080 ‫document, query, aggregate, and model middleware. 24 00:01:10,080 --> 00:01:12,110 ‫And in this lecture, we're gonna talk about 25 00:01:12,110 --> 00:01:14,410 ‫document middleware, which is middleware 26 00:01:14,410 --> 00:01:18,110 ‫that can act on the currently processed document. 27 00:01:18,110 --> 00:01:20,920 ‫So just like the virtual properties, 28 00:01:20,920 --> 00:01:23,613 ‫we define a middleware on the schema, 29 00:01:25,800 --> 00:01:28,543 ‫so tourSchema.pre. 30 00:01:30,030 --> 00:01:32,850 ‫And so this is for pre middleware, which again, 31 00:01:32,850 --> 00:01:35,450 ‫is gonna run before an actual event. 32 00:01:35,450 --> 00:01:39,360 ‫And that event in this case is the save event. 33 00:01:39,360 --> 00:01:41,350 ‫And so this call back function that we're 34 00:01:41,350 --> 00:01:42,613 ‫gonna define here next, 35 00:01:43,870 --> 00:01:44,820 ‫so function 36 00:01:48,200 --> 00:01:51,980 ‫so this function will be called before an actual document 37 00:01:51,980 --> 00:01:53,943 ‫is saved to the database. 38 00:01:55,407 --> 00:02:00,407 ‫So this is document middleware, 39 00:02:02,010 --> 00:02:05,910 ‫and it runs, let me write all of that here. 40 00:02:05,910 --> 00:02:09,640 ‫So it runs before the save command 41 00:02:10,550 --> 00:02:13,953 ‫and the .create command. 42 00:02:14,860 --> 00:02:17,040 ‫But not on insert many. 43 00:02:17,040 --> 00:02:22,040 ‫So if we use this command here, so insertMany, 44 00:02:22,450 --> 00:02:26,153 ‫then that will actually not trigger the save middleware. 45 00:02:27,600 --> 00:02:29,140 ‫So always keep that in mind. 46 00:02:29,140 --> 00:02:32,780 ‫It's very important to realize that only on save 47 00:02:32,780 --> 00:02:35,560 ‫and on create actually this middleware here 48 00:02:35,560 --> 00:02:36,943 ‫is gonna be executed. 49 00:02:38,929 --> 00:02:41,740 ‫And so let's start by doing a simple console.log 50 00:02:42,670 --> 00:02:45,253 ‫and what I'm gonna log through the console is this. 51 00:02:46,350 --> 00:02:49,870 ‫And so in a save middleware, the disk keyword here 52 00:02:49,870 --> 00:02:53,100 ‫is gonna point to the currently processed document. 53 00:02:53,100 --> 00:02:56,640 ‫And that is the reason why it is called document middleware. 54 00:02:56,640 --> 00:02:58,740 ‫Again, because in this function here, 55 00:02:58,740 --> 00:03:02,470 ‫we have access to the document that is being processed. 56 00:03:02,470 --> 00:03:05,133 ‫So in this case, the document that is being saved. 57 00:03:06,078 --> 00:03:09,240 ‫And so let me just very quickly show that to you 58 00:03:09,240 --> 00:03:11,300 ‫using this console.log. 59 00:03:11,300 --> 00:03:13,610 ‫And so in order to now trigger this function, 60 00:03:13,610 --> 00:03:17,800 ‫remember we need to run a save command or a create command. 61 00:03:17,800 --> 00:03:22,020 ‫And so we now need to create a new tour using our API 62 00:03:22,020 --> 00:03:26,013 ‫in order to, yeah, to then trigger this middleware. 63 00:03:27,680 --> 00:03:32,680 ‫So let's go here to, to postman, and I'm gonna start by 64 00:03:33,880 --> 00:03:36,830 ‫by saving these two new routes that we created 65 00:03:38,450 --> 00:03:42,313 ‫in the previous lectures, so get monthly plan. 66 00:03:47,300 --> 00:03:52,300 ‫And this one here is get tour stats. 67 00:03:56,031 --> 00:03:59,523 ‫So now I can close them and create new tour. 68 00:04:00,430 --> 00:04:03,060 ‫And we specify the data here in the body. 69 00:04:03,060 --> 00:04:06,300 ‫Now not all of the stuff here is actually required, 70 00:04:06,300 --> 00:04:08,730 ‫so let's take a look at what actually is required 71 00:04:08,730 --> 00:04:11,040 ‫and get rid of the rest. 72 00:04:11,040 --> 00:04:13,483 ‫So the imageCover is required, the summary, 73 00:04:14,610 --> 00:04:18,500 ‫of course the price, and yeah. 74 00:04:18,500 --> 00:04:20,830 ‫So let's get rid of the stuff that we don't 75 00:04:21,760 --> 00:04:24,483 ‫really need here just to keep it at a minimum. 76 00:04:26,000 --> 00:04:28,730 ‫So the ratings, quantity, average, 77 00:04:28,730 --> 00:04:30,080 ‫so these are not necessary. 78 00:04:36,550 --> 00:04:38,490 ‫So I'm just gonna call this one here 79 00:04:38,490 --> 00:04:43,490 ‫the test tour, just to keep it really simple here. 80 00:04:45,702 --> 00:04:49,370 ‫Now let's send this request and indeed, 81 00:04:49,370 --> 00:04:52,420 ‫it created the new document and now let's take a look 82 00:04:52,420 --> 00:04:56,370 ‫at our console and see that document here. 83 00:04:56,370 --> 00:04:58,650 ‫And indeed, here it is. 84 00:04:58,650 --> 00:05:01,540 ‫So let's increase this here a little bit 85 00:05:01,540 --> 00:05:04,900 ‫and so this is what our document is looking like 86 00:05:04,900 --> 00:05:08,510 ‫right before it saved into the database. 87 00:05:08,510 --> 00:05:11,710 ‫And so here we have ratingsAverage and quantity, 88 00:05:11,710 --> 00:05:13,500 ‫which are set by default. 89 00:05:13,500 --> 00:05:17,077 ‫Remember, so 4.5 and zero, and then 90 00:05:19,185 --> 00:05:21,930 ‫the createdAt time stamp, and you can even 91 00:05:21,930 --> 00:05:24,523 ‫see the virtual property that we defined here. 92 00:05:25,700 --> 00:05:28,100 ‫So again, this is right before we actually 93 00:05:28,100 --> 00:05:30,140 ‫save this data to the database. 94 00:05:30,140 --> 00:05:31,410 ‫And so at this point of time, 95 00:05:31,410 --> 00:05:34,600 ‫we can still act on the data before it is then saved 96 00:05:34,600 --> 00:05:36,920 ‫to the database and that is exactly 97 00:05:36,920 --> 00:05:38,173 ‫what we're gonna do now. 98 00:05:39,520 --> 00:05:43,240 ‫So down here in our middleware function. 99 00:05:43,240 --> 00:05:45,900 ‫And what I wanna do here is to create a slug 100 00:05:45,900 --> 00:05:48,120 ‫for each of these documents. 101 00:05:48,120 --> 00:05:50,080 ‫So remember how in the first section, 102 00:05:50,080 --> 00:05:52,510 ‫we created a slug for each of the products 103 00:05:52,510 --> 00:05:54,313 ‫that we had in the store. 104 00:05:55,180 --> 00:05:57,860 ‫And so a slug is basically just a string 105 00:05:57,860 --> 00:06:01,590 ‫that we can put in the URL, usually based on 106 00:06:01,590 --> 00:06:03,570 ‫some string like the name. 107 00:06:03,570 --> 00:06:05,780 ‫So in this case, we're gonna create a slug 108 00:06:05,780 --> 00:06:07,433 ‫based here on the tour name. 109 00:06:09,150 --> 00:06:14,150 ‫So remember how for that we used the slugify package. 110 00:06:14,210 --> 00:06:16,360 ‫And so let's now go ahead and install that. 111 00:06:20,120 --> 00:06:22,063 ‫All right, and while that's doing, 112 00:06:23,430 --> 00:06:25,743 ‫let's go ahead and then require it here. 113 00:06:33,270 --> 00:06:34,980 ‫So require slugify. 114 00:06:39,100 --> 00:06:41,893 ‫Let's go back to our first window here, actually. 115 00:06:43,530 --> 00:06:46,220 ‫And now, down here, we no longer want 116 00:06:46,220 --> 00:06:48,550 ‫to log this to the console. 117 00:06:48,550 --> 00:06:51,720 ‫But instead we can now say this, and remember, 118 00:06:51,720 --> 00:06:54,840 ‫this is the currently processed document. 119 00:06:54,840 --> 00:06:58,060 ‫So we can now define a new property on it. 120 00:06:58,060 --> 00:06:59,860 ‫And that's exactly what I'm doing. 121 00:06:59,860 --> 00:07:03,250 ‫So this.slug should be slugify, 122 00:07:06,210 --> 00:07:08,390 ‫and then just a string that we want to create 123 00:07:08,390 --> 00:07:13,390 ‫a slug out of, and so that's gonna be this.name 124 00:07:13,470 --> 00:07:15,890 ‫and then we also want to pass in the option 125 00:07:15,890 --> 00:07:18,653 ‫that everything should be converted to lower case, 126 00:07:19,970 --> 00:07:24,220 ‫and so that's lower: true, and now I'll give it a save. 127 00:07:24,220 --> 00:07:26,290 ‫And one thing that we didn't talk about yet 128 00:07:26,290 --> 00:07:28,710 ‫is the next function. 129 00:07:28,710 --> 00:07:32,440 ‫So just like in Express, we also have the next function 130 00:07:32,440 --> 00:07:35,300 ‫in mMngoose middleware, basically to call the next 131 00:07:35,300 --> 00:07:37,780 ‫middleware in the stack as we already know. 132 00:07:37,780 --> 00:07:40,680 ‫Now in this case, we only have one middleware function, 133 00:07:40,680 --> 00:07:43,100 ‫which is why we didn't run into any problems, 134 00:07:43,100 --> 00:07:46,433 ‫even not calling next, but let's actually now do that. 135 00:07:47,470 --> 00:07:50,040 ‫And so each middleware function, in a pre save 136 00:07:50,040 --> 00:07:52,723 ‫middleware has access to next. 137 00:07:54,492 --> 00:07:57,700 ‫So that's exactly the same as in Express, 138 00:07:57,700 --> 00:08:01,070 ‫and so by the end of the middleware we call next, 139 00:08:01,070 --> 00:08:03,300 ‫and that will then call the next middleware 140 00:08:03,300 --> 00:08:04,583 ‫in the stack. 141 00:08:04,583 --> 00:08:07,540 ‫So let's try this out again. 142 00:08:07,540 --> 00:08:10,556 ‫And this is gonna be called test tour number two. 143 00:08:10,556 --> 00:08:13,770 ‫Very simple, send to sky, 144 00:08:13,770 --> 00:08:16,900 ‫and let's wait for it. 145 00:08:16,900 --> 00:08:20,930 ‫And now for some reason, it's not really here. 146 00:08:20,930 --> 00:08:22,950 ‫Let's see if we got some error, 147 00:08:22,950 --> 00:08:24,630 ‫and we actually did not. 148 00:08:24,630 --> 00:08:27,570 ‫But the reason why it's not working 149 00:08:27,570 --> 00:08:31,913 ‫is that right now we don't have any slug in our schema. 150 00:08:31,913 --> 00:08:35,360 ‫And remember this actually happened to us before 151 00:08:35,360 --> 00:08:38,150 ‫when we only had a couple of fields in the schema. 152 00:08:38,150 --> 00:08:40,150 ‫And when we, then we'll define some fields 153 00:08:40,150 --> 00:08:42,450 ‫that were not in the schema, then they were 154 00:08:42,450 --> 00:08:44,770 ‫simply not persisted to the database. 155 00:08:44,770 --> 00:08:47,070 ‫And the same thing is now happening here, 156 00:08:47,070 --> 00:08:50,670 ‫so we defined the slug property, but it's not in our schema. 157 00:08:50,670 --> 00:08:54,200 ‫And therefore it was then not saved to the database, 158 00:08:54,200 --> 00:08:56,990 ‫and so let's quickly fix that and let's put it, 159 00:08:56,990 --> 00:08:59,490 ‫oh, I don't know, it doesn't really matter, 160 00:08:59,490 --> 00:09:01,373 ‫can put it here right after the name, 161 00:09:03,210 --> 00:09:06,253 ‫so the slug should simply be a string. 162 00:09:08,443 --> 00:09:10,363 ‫And so that should fix it. 163 00:09:11,610 --> 00:09:14,823 ‫So let's go back and create the test tour number three. 164 00:09:15,880 --> 00:09:18,220 ‫Because it cannot be the same, because remember 165 00:09:18,220 --> 00:09:20,453 ‫we cannot have tours with the same name. 166 00:09:22,260 --> 00:09:26,290 ‫So do it again, and now indeed we have the slug property 167 00:09:26,290 --> 00:09:29,900 ‫right here and it is indeed based on the name, 168 00:09:29,900 --> 00:09:31,170 ‫as you can see here. 169 00:09:31,170 --> 00:09:33,853 ‫Great, so let's go back here, 170 00:09:34,770 --> 00:09:36,463 ‫gonna reduce this a little bit. 171 00:09:37,480 --> 00:09:40,957 ‫And so here we have the pre document middleware. 172 00:09:40,957 --> 00:09:44,000 ‫Let's now just very quickly experiment, also, 173 00:09:44,000 --> 00:09:45,593 ‫with a post middleware. 174 00:09:47,700 --> 00:09:52,700 ‫So tourSchema.post and let's use save again. 175 00:09:55,487 --> 00:09:58,740 ‫And then the callback function, 176 00:09:58,740 --> 00:10:01,090 ‫which in the case of post middleware 177 00:10:01,090 --> 00:10:03,860 ‫has access not only to next, but also to 178 00:10:03,860 --> 00:10:06,823 ‫the document that was just saved to the database. 179 00:10:07,690 --> 00:10:10,883 ‫So let's call that one doc and then next. 180 00:10:12,193 --> 00:10:14,650 ‫And so post middleware functions 181 00:10:14,650 --> 00:10:17,750 ‫are executed after all the pre middleware functions 182 00:10:17,750 --> 00:10:20,090 ‫have completed, all right. 183 00:10:20,090 --> 00:10:23,440 ‫So in here we actually no longer have the disk keyword, 184 00:10:23,440 --> 00:10:25,910 ‫but instead we have the basically finished 185 00:10:25,910 --> 00:10:27,853 ‫document here in doc. 186 00:10:30,960 --> 00:10:34,650 ‫So let's just log that finished document 187 00:10:34,650 --> 00:10:37,640 ‫to the console and then call next. 188 00:10:37,640 --> 00:10:39,713 ‫Now in this case again, we only have one 189 00:10:39,713 --> 00:10:43,200 ‫post middleware and so we wouldn't really need next, 190 00:10:43,200 --> 00:10:46,860 ‫but it's a best practice to simply always include it. 191 00:10:46,860 --> 00:10:50,310 ‫Now another thing that I wanted to show you 192 00:10:50,310 --> 00:10:52,470 ‫is that we can have, of course, multiple 193 00:10:52,470 --> 00:10:56,283 ‫pre middlewares or also post middlewares for the same hook. 194 00:10:57,270 --> 00:11:01,820 ‫And hook is what we call this save here. 195 00:11:01,820 --> 00:11:04,690 ‫So this middleware here is basically what we call 196 00:11:04,690 --> 00:11:07,810 ‫a pre save hook. 197 00:11:07,810 --> 00:11:11,490 ‫So you will see that terminology all the time. 198 00:11:11,490 --> 00:11:14,173 ‫So some call it middleware, and some call it hooks. 199 00:11:15,270 --> 00:11:17,260 ‫And so this is gonna be a pre save hook 200 00:11:17,260 --> 00:11:18,773 ‫or pre save middleware. 201 00:11:21,880 --> 00:11:25,823 ‫So function, and this one has access to next. 202 00:11:28,770 --> 00:11:31,433 ‫And so let's just log something to the console here, 203 00:11:33,780 --> 00:11:37,963 ‫like will save document. 204 00:11:40,740 --> 00:11:45,023 ‫And then next, and that of course, should be next. 205 00:11:46,880 --> 00:11:48,750 ‫Just to see if we get some error, 206 00:11:48,750 --> 00:11:50,653 ‫I'm gonna omit the next here. 207 00:11:51,490 --> 00:11:55,283 ‫Just to see what happens when we do not call it. 208 00:11:57,290 --> 00:11:59,080 ‫So I'm gonna create a new tour, 209 00:11:59,080 --> 00:12:01,230 ‫and by the end of this lecture I'm gonna delete 210 00:12:01,230 --> 00:12:04,543 ‫all of them, but for now we need them here. 211 00:12:06,410 --> 00:12:09,930 ‫And so now you see that it's not really finishing, 212 00:12:09,930 --> 00:12:12,620 ‫so we're stuck in that one middleware function 213 00:12:12,620 --> 00:12:14,473 ‫that doesn't have the next call. 214 00:12:16,410 --> 00:12:18,343 ‫So basically we're stuck in here. 215 00:12:19,550 --> 00:12:20,970 ‫So let's cancel the request 216 00:12:22,810 --> 00:12:25,780 ‫and then get it back here, 217 00:12:25,780 --> 00:12:27,173 ‫and try that again. 218 00:12:29,550 --> 00:12:32,070 ‫And so now it worked indeed. 219 00:12:32,070 --> 00:12:35,740 ‫So our slug is here, right, 220 00:12:35,740 --> 00:12:38,590 ‫and so let's take a look at our console, 221 00:12:38,590 --> 00:12:41,973 ‫and so indeed, our second pre middleware also run, 222 00:12:42,850 --> 00:12:45,797 ‫so the one logging will save document and then 223 00:12:45,797 --> 00:12:49,320 ‫our post middleware then logged to the console 224 00:12:49,320 --> 00:12:51,570 ‫the final document, and so that should also 225 00:12:51,570 --> 00:12:55,043 ‫already have the slug and yeah, here it is. 226 00:12:56,050 --> 00:12:57,870 ‫And that's actually all I had to show you 227 00:12:57,870 --> 00:13:00,360 ‫about document middleware. 228 00:13:00,360 --> 00:13:03,065 ‫Now I'm just gonna comment out these two here 229 00:13:03,065 --> 00:13:06,680 ‫because I don't want to pollute my log here 230 00:13:06,680 --> 00:13:09,110 ‫all the time with these console.logs, 231 00:13:09,110 --> 00:13:11,190 ‫but I'm still keeping them here, again, 232 00:13:11,190 --> 00:13:12,173 ‫as a reference. 233 00:13:13,530 --> 00:13:16,330 ‫So what I want you to remember from this lecture 234 00:13:16,330 --> 00:13:18,980 ‫is that we can have middleware running before 235 00:13:18,980 --> 00:13:20,930 ‫and after a certain event. 236 00:13:20,930 --> 00:13:23,160 ‫And in the case of document middleware, 237 00:13:23,160 --> 00:13:25,850 ‫that event is usually the save event. 238 00:13:25,850 --> 00:13:29,260 ‫And then in the middleware function itself, 239 00:13:29,260 --> 00:13:31,660 ‫we have access to the disk keyword, 240 00:13:31,660 --> 00:13:35,163 ‫which is gonna point at the currently being saved document. 241 00:13:36,190 --> 00:13:38,232 ‫And it's also very important to keep in mind 242 00:13:38,232 --> 00:13:42,650 ‫that this save middleware only runs for the save 243 00:13:42,650 --> 00:13:44,650 ‫and create Mongoose methods. 244 00:13:44,650 --> 00:13:47,690 ‫It's not gonna run, for example, for insert many 245 00:13:47,690 --> 00:13:50,490 ‫and also not for find one and update 246 00:13:50,490 --> 00:13:54,380 ‫or find by ID and update, which we already used before. 247 00:13:54,380 --> 00:13:58,110 ‫So for example, we somewhere here we have 248 00:14:00,870 --> 00:14:04,960 ‫we have findByIdAndUpdate, but that is not gonna trigger 249 00:14:04,960 --> 00:14:06,862 ‫this save middleware. 250 00:14:06,862 --> 00:14:09,610 ‫So that's very important to keep in mind 251 00:14:09,610 --> 00:14:11,550 ‫because actually a bit later in this project, 252 00:14:11,550 --> 00:14:14,950 ‫we will have to work around that limitation. 253 00:14:14,950 --> 00:14:17,160 ‫All right, so this is document middleware 254 00:14:17,160 --> 00:14:20,880 ‫to manipulate documents that are currently being saved. 255 00:14:20,880 --> 00:14:23,833 ‫Next up, we're gonna talk about query middleware.