1 00:00:01,693 --> 00:00:04,860 Now, this was our first API, 2 00:00:04,860 --> 00:00:07,810 our first basic API that we built. 3 00:00:07,810 --> 00:00:10,620 Now, we will move on to a different example, 4 00:00:10,620 --> 00:00:12,810 a different API which we'll build, 5 00:00:12,810 --> 00:00:15,110 which will be a little bit more complex 6 00:00:15,110 --> 00:00:19,163 and where we will see more than just GET routes in action. 7 00:00:20,040 --> 00:00:21,470 Here, we are going to build 8 00:00:21,470 --> 00:00:24,410 a Simple Todo Management Web API, 9 00:00:24,410 --> 00:00:26,650 and therefore in the end Web App 10 00:00:26,650 --> 00:00:28,660 because I will later also provide you 11 00:00:28,660 --> 00:00:30,350 with a decoupled frontend, 12 00:00:30,350 --> 00:00:33,180 but we're going to start with the API. 13 00:00:33,180 --> 00:00:36,110 And the goal of this API which we build 14 00:00:36,110 --> 00:00:40,263 is that we allow users of this API to manage todos. 15 00:00:41,210 --> 00:00:43,450 For this, we'll have a GET route to /todos 16 00:00:44,780 --> 00:00:47,210 which should retrieve and return a list 17 00:00:47,210 --> 00:00:50,390 of all the todos that are stored in the database. 18 00:00:50,390 --> 00:00:52,260 And for this API here, 19 00:00:52,260 --> 00:00:56,960 we can say that a todo is simply a document, an object, 20 00:00:56,960 --> 00:01:00,423 which contains the todo text and a unique id. 21 00:01:01,410 --> 00:01:05,650 We'll have a POST /todos route, an endpoint therefore, 22 00:01:05,650 --> 00:01:08,090 which will accept incoming data, 23 00:01:08,090 --> 00:01:10,620 so where the request should contain some data 24 00:01:10,620 --> 00:01:13,530 in the request body in the JSON format, 25 00:01:13,530 --> 00:01:14,800 which we will parse 26 00:01:14,800 --> 00:01:18,270 and then store as a new todo in the database. 27 00:01:18,270 --> 00:01:21,120 And, of course, you wanna return a success response, 28 00:01:21,120 --> 00:01:25,890 maybe with that newly created todo in the response body. 29 00:01:25,890 --> 00:01:28,100 And then I got two more routes, 30 00:01:28,100 --> 00:01:31,870 for example, a PATCH route where we target a specific todo 31 00:01:31,870 --> 00:01:36,750 with /todos and then slash the id of a specific todo 32 00:01:36,750 --> 00:01:39,333 to update the text of an existing todo, 33 00:01:40,470 --> 00:01:45,470 and we'll have a DELETE /todos/ some specific id route 34 00:01:46,010 --> 00:01:48,610 which allows us to delete a todo, 35 00:01:48,610 --> 00:01:51,860 so that we have all these CRUD operations at this example 36 00:01:51,860 --> 00:01:54,010 of this basic todos app here 37 00:01:54,010 --> 00:01:57,240 or of this basic todos API here. 38 00:01:57,240 --> 00:02:00,720 Now, that's the next API we'll build, and as I mentioned, 39 00:02:00,720 --> 00:02:04,190 later I will also provide you with a fitting frontend, 40 00:02:04,190 --> 00:02:08,460 some JavaScript code, browser-side JavaScript code, 41 00:02:08,460 --> 00:02:10,610 that will talk to this API, 42 00:02:10,610 --> 00:02:12,070 but that will be the next step. 43 00:02:12,070 --> 00:02:14,570 First of all, we're going to build it. 44 00:02:14,570 --> 00:02:16,550 Now, to build this API, 45 00:02:16,550 --> 00:02:21,550 I got a brand new project here which you also find attached 46 00:02:21,600 --> 00:02:24,740 where I got an empty models and controllers 47 00:02:24,740 --> 00:02:26,130 and routes folder. 48 00:02:26,130 --> 00:02:29,420 You'll have to create those folders on your own. 49 00:02:29,420 --> 00:02:30,300 In the data folder, 50 00:02:30,300 --> 00:02:33,700 I got the database.js file where we connect to a database 51 00:02:33,700 --> 00:02:37,690 now to the second-api database on the database server, 52 00:02:37,690 --> 00:02:40,090 which you therefore, of course, need to start. 53 00:02:40,090 --> 00:02:43,450 You need to have MongoDB installed and started. 54 00:02:43,450 --> 00:02:46,260 And then app.js has just got some basic setup. 55 00:02:46,260 --> 00:02:49,540 I got no routes yet because we'll add those together, 56 00:02:49,540 --> 00:02:52,290 and I also got no model and nothing like this. 57 00:02:52,290 --> 00:02:55,510 We're all going to add this together. 58 00:02:55,510 --> 00:02:57,580 Now, if you download this snapshot, 59 00:02:57,580 --> 00:02:59,480 you will have to run npm install 60 00:02:59,480 --> 00:03:02,500 so that you get this node_modules folder. 61 00:03:02,500 --> 00:03:04,450 And then you could run npm start, 62 00:03:04,450 --> 00:03:06,840 but, first of all, I'm going to write some code here 63 00:03:06,840 --> 00:03:10,553 and add some logic to this web API before I'll start it. 64 00:03:11,520 --> 00:03:16,180 And I'll start by adding a model, the todo.model.js file, 65 00:03:16,180 --> 00:03:19,020 where I wanna add a Todo class 66 00:03:20,130 --> 00:03:22,573 which helps us store and create todos. 67 00:03:23,810 --> 00:03:26,430 For this here, I will add a constructor 68 00:03:26,430 --> 00:03:28,900 which is this method which is called automatically 69 00:03:28,900 --> 00:03:32,470 when a new instance of this class is created. 70 00:03:32,470 --> 00:03:35,480 And here I expect to get the todo text 71 00:03:35,480 --> 00:03:37,010 so that in the constructor, 72 00:03:37,010 --> 00:03:42,010 I can add it as a text property to the to-be created object. 73 00:03:42,330 --> 00:03:45,540 And, of course, we can already also export this Todo class 74 00:03:45,540 --> 00:03:48,123 so that later we can use it outside of this file. 75 00:03:49,550 --> 00:03:52,550 Now, eventually, I want to be able to save my todos 76 00:03:52,550 --> 00:03:57,550 which exist as objects in my running web application here 77 00:03:57,570 --> 00:03:58,940 to the database. 78 00:03:58,940 --> 00:04:00,870 And for this, I'll add a save method 79 00:04:00,870 --> 00:04:04,290 as we did it before in the course for other examples 80 00:04:04,290 --> 00:04:06,490 like the online shop as well. 81 00:04:06,490 --> 00:04:08,150 And in this save method, 82 00:04:08,150 --> 00:04:10,970 I, of course, wanna reach out to the database 83 00:04:10,970 --> 00:04:14,330 so I will actually require my database file 84 00:04:14,330 --> 00:04:16,089 from the data folder here 85 00:04:16,089 --> 00:04:19,300 and import this db object 86 00:04:19,300 --> 00:04:23,000 so that here I can then run get.Db, 87 00:04:23,000 --> 00:04:27,780 reach out to a collection, let's say the todos collection, 88 00:04:27,780 --> 00:04:32,780 and then there, I want to insert one new todo. 89 00:04:34,890 --> 00:04:37,270 Now, for this todo which I wanna insert, 90 00:04:37,270 --> 00:04:39,810 I only wanna add a text property 91 00:04:39,810 --> 00:04:42,220 to this document that should be inserted, 92 00:04:42,220 --> 00:04:44,633 and I'll set this equal to this.text. 93 00:04:46,040 --> 00:04:47,770 Now, this will return a promise, 94 00:04:47,770 --> 00:04:50,370 and hence we could turn this into a async function 95 00:04:50,370 --> 00:04:51,820 and await this, 96 00:04:51,820 --> 00:04:55,360 but here I'll just return this so that I return this promise 97 00:04:55,360 --> 00:04:57,570 which is returned by this line of code 98 00:04:57,570 --> 00:04:59,393 as part of this save method. 99 00:05:00,890 --> 00:05:03,380 Of course, this is actually only the correct code 100 00:05:03,380 --> 00:05:05,240 if we're creating a new todo, 101 00:05:05,240 --> 00:05:09,540 so I also want to have code that updates an existing todo, 102 00:05:09,540 --> 00:05:13,293 just as we also had it before in other parts of this course. 103 00:05:14,230 --> 00:05:15,700 For this in a constructor, 104 00:05:15,700 --> 00:05:19,170 I will actually accept an id as a second parameter, 105 00:05:19,170 --> 00:05:21,580 though this might not always be provided. 106 00:05:21,580 --> 00:05:25,280 If we create a todo for the first time, we won't have an id, 107 00:05:25,280 --> 00:05:28,690 hence no value for this parameter will be provided, 108 00:05:28,690 --> 00:05:31,700 and therefore id will be undefined, 109 00:05:31,700 --> 00:05:35,980 but I will still store it, and it might be defined. 110 00:05:35,980 --> 00:05:37,910 And because it might be defined 111 00:05:37,910 --> 00:05:40,010 but isn't guaranteed to be defined, 112 00:05:40,010 --> 00:05:43,890 here in the save method, I'll check if this id is truthy, 113 00:05:43,890 --> 00:05:46,040 which means it does exist, 114 00:05:46,040 --> 00:05:48,510 which means I wanna update an existing todo 115 00:05:48,510 --> 00:05:52,170 because I have an id already and I'm calling save 116 00:05:52,170 --> 00:05:54,533 so I must be updating an existing todo. 117 00:05:55,680 --> 00:05:58,070 Else, if we have no id and we call save, 118 00:05:58,070 --> 00:05:59,620 we are creating a new todo, 119 00:05:59,620 --> 00:06:02,620 and that's therefore when I wanna execute this line of code. 120 00:06:03,840 --> 00:06:06,220 Here in this first branch of the if block, 121 00:06:06,220 --> 00:06:08,993 I will instead return db.getDb, 122 00:06:09,870 --> 00:06:13,060 reaching out to the todos collection as always, 123 00:06:13,060 --> 00:06:16,313 and then here we call updateOne to update a todo. 124 00:06:18,340 --> 00:06:20,520 Now, for this, I need the id of the todo, 125 00:06:20,520 --> 00:06:23,802 and I'll transform this to a mongodb.ObjectId 126 00:06:23,802 --> 00:06:26,260 so that we'll never run into problems there, 127 00:06:26,260 --> 00:06:31,260 and hence I'll require mongodb here in this file. 128 00:06:32,450 --> 00:06:33,960 And then in the save method, 129 00:06:33,960 --> 00:06:38,150 we can get our todoId as an object id 130 00:06:38,150 --> 00:06:41,720 by using new mongodb.ObjectId 131 00:06:41,720 --> 00:06:43,170 and passing this id, 132 00:06:43,170 --> 00:06:46,830 which we know exists in this part here, in this if branch, 133 00:06:46,830 --> 00:06:49,110 to object id. 134 00:06:49,110 --> 00:06:51,480 So then I get the todo as an object id, 135 00:06:51,480 --> 00:06:55,610 and hence here for updateOne for the first-parameter value, 136 00:06:55,610 --> 00:06:58,670 I described my filtering condition, 137 00:06:58,670 --> 00:07:02,970 and I'm looking for a document where _id in the database, 138 00:07:02,970 --> 00:07:07,630 because that's the default id field MongoDB will add 139 00:07:07,630 --> 00:07:11,160 to every document that's inserted in the database, 140 00:07:11,160 --> 00:07:14,467 so where _id is equal to todoId. 141 00:07:16,310 --> 00:07:20,140 And then with the second-parameter value here for updateOne, 142 00:07:20,140 --> 00:07:22,080 we describe the update, 143 00:07:22,080 --> 00:07:27,080 and here I'll just add this special $set key 144 00:07:27,370 --> 00:07:30,090 where we then pass an object that describes 145 00:07:30,090 --> 00:07:33,030 which keys or which fields in the document 146 00:07:33,030 --> 00:07:36,350 should be updated with which values. 147 00:07:36,350 --> 00:07:38,650 And here I wanna update the text field 148 00:07:38,650 --> 00:07:42,600 in the document that was identified with this condition 149 00:07:42,600 --> 00:07:45,563 with the text that's stored in this text. 150 00:07:46,480 --> 00:07:48,883 So that's then my updating logic here. 151 00:07:51,450 --> 00:07:54,010 With that, I got this save method. 152 00:07:54,010 --> 00:07:57,333 Of course, we will also need a method for deleting a todo, 153 00:07:58,170 --> 00:08:02,350 and therefore I'll add a delete method here at the bottom, 154 00:08:02,350 --> 00:08:05,070 though you know the position doesn't matter. 155 00:08:05,070 --> 00:08:08,230 And here we could check if we maybe don't have an id, 156 00:08:08,230 --> 00:08:10,590 which means we try to delete a todo 157 00:08:10,590 --> 00:08:13,420 which doesn't exist in the database yet 158 00:08:13,420 --> 00:08:16,230 in which case we could throw a new error, 159 00:08:16,230 --> 00:08:18,530 though that's totally optional, 160 00:08:18,530 --> 00:08:23,530 where I say Trying to delete todo without id! 161 00:08:24,320 --> 00:08:27,400 It is a case that actually shouldn't occur in our API 162 00:08:27,400 --> 00:08:29,730 since we will write code that ensures 163 00:08:29,730 --> 00:08:33,960 that we only call delete on todos that we do have, 164 00:08:33,960 --> 00:08:36,823 but nonetheless this is extra check you could add. 165 00:08:38,039 --> 00:08:40,549 More importantly, though, after this check, 166 00:08:40,549 --> 00:08:43,190 we wanna actually delete the todo, 167 00:08:43,190 --> 00:08:45,180 and therefore what I'll do here 168 00:08:45,180 --> 00:08:48,453 is I will return db.getDb, 169 00:08:49,630 --> 00:08:53,810 reaching out to the todos collection as always, 170 00:08:53,810 --> 00:08:58,100 and here we can call deleteOne to delete one document, 171 00:08:58,100 --> 00:09:00,700 and we need to provide our filtering condition here. 172 00:09:01,610 --> 00:09:03,280 And now just as before, 173 00:09:03,280 --> 00:09:06,880 for this, I wanna create a todoId as an object id, 174 00:09:06,880 --> 00:09:10,860 so I will copy this line of code and add that here. 175 00:09:10,860 --> 00:09:13,000 And then I wanna delete the todo 176 00:09:13,000 --> 00:09:17,343 where _id is equal to this.todoId, like that. 177 00:09:20,098 --> 00:09:23,550 So that's the delete method which should do the trick. 178 00:09:23,550 --> 00:09:28,550 Now, we also wanna add static methods for fetching todos 179 00:09:29,050 --> 00:09:32,153 or one static method for fetching all the todos. 180 00:09:33,280 --> 00:09:35,920 For this, I'll add a static method getTodos 181 00:09:37,220 --> 00:09:41,330 or getAllTodos, however you wanna name it. 182 00:09:41,330 --> 00:09:45,553 And here I return db.getDb collection todos, 183 00:09:46,750 --> 00:09:49,730 and we simply find all todos here, 184 00:09:49,730 --> 00:09:53,210 but, actually, I wanna do a bit more than that. 185 00:09:53,210 --> 00:09:55,740 I also wanna get them as an array, 186 00:09:55,740 --> 00:09:57,930 as we did it before in the course as well, 187 00:09:57,930 --> 00:10:01,240 but I also wanna transform all these todo documents 188 00:10:01,240 --> 00:10:03,050 which we get from the collection 189 00:10:03,050 --> 00:10:07,380 into objects that are instantiated like this, 190 00:10:07,380 --> 00:10:09,943 so that are instantiated with help of this class. 191 00:10:11,250 --> 00:10:14,980 Therefore, I will actually turn this into a async method 192 00:10:14,980 --> 00:10:18,530 so that I can get my todoDocuments here 193 00:10:18,530 --> 00:10:20,900 by awaiting this operation, 194 00:10:20,900 --> 00:10:23,753 and then in the next step, I can transform them all. 195 00:10:24,800 --> 00:10:29,380 So here we can then return todoDocuments and call map. 196 00:10:29,380 --> 00:10:32,170 You learned that the map method is a built-in method 197 00:10:32,170 --> 00:10:34,530 that exists on JavaScript arrays 198 00:10:34,530 --> 00:10:37,833 which allows us to transform all the elements in an array. 199 00:10:39,190 --> 00:10:41,870 And for this, we get an anonymous function here 200 00:10:41,870 --> 00:10:43,220 which gets the todoDocument 201 00:10:44,460 --> 00:10:46,940 because this function will automatically execute 202 00:10:46,940 --> 00:10:49,299 for all the todoDocuments. 203 00:10:49,299 --> 00:10:51,950 And then here, in this anonymous function, 204 00:10:51,950 --> 00:10:54,490 I return my transformed object. 205 00:10:54,490 --> 00:10:58,800 And for this, I'll instantiate my class here, my Todo class, 206 00:10:58,800 --> 00:11:00,440 with new Todo, 207 00:11:00,440 --> 00:11:05,440 and I pass in these two constructor values, text and id, 208 00:11:05,880 --> 00:11:09,910 which is todoDocument._id 209 00:11:09,910 --> 00:11:13,363 and todoDocument.text, 210 00:11:14,680 --> 00:11:15,513 like this. 211 00:11:16,840 --> 00:11:20,350 So this will now return these transformed todos, 212 00:11:20,350 --> 00:11:23,233 and that's my getAllTodos method which I need here. 213 00:11:25,240 --> 00:11:28,460 With that done, the model should be finished. 214 00:11:28,460 --> 00:11:30,920 We'll see if we need to fix an error later. 215 00:11:30,920 --> 00:11:32,580 It looks good though. 216 00:11:32,580 --> 00:11:34,570 Now, we can add a controller, 217 00:11:34,570 --> 00:11:38,640 the todos.controller.js file here, 218 00:11:38,640 --> 00:11:43,500 where I wanna add a function for getting all the todos 219 00:11:45,680 --> 00:11:50,200 and then also a function for adding a todo, 220 00:11:50,200 --> 00:11:52,010 so I'll add all these actions right now, 221 00:11:52,010 --> 00:11:55,800 and we're then going to populate them with more life later, 222 00:11:55,800 --> 00:11:57,693 then a function for updating a todo, 223 00:11:58,770 --> 00:12:03,770 and then also a function for deleting a todo, 224 00:12:03,950 --> 00:12:05,693 so for these CRUD operations. 225 00:12:06,930 --> 00:12:10,580 And, of course, all these functions should be exposed, 226 00:12:10,580 --> 00:12:12,750 so I will export an object here 227 00:12:12,750 --> 00:12:15,210 where I will add all these functions as keys 228 00:12:15,210 --> 00:12:17,290 and then point at all these functions 229 00:12:17,290 --> 00:12:21,800 so that they are available outside of this file here as well 230 00:12:21,800 --> 00:12:26,223 with addTodo, updateTodo, deleteTodo, and so on. 231 00:12:28,160 --> 00:12:30,150 And then, of course, all these functions 232 00:12:30,150 --> 00:12:32,690 will get request, response, and next 233 00:12:32,690 --> 00:12:34,830 because they are controller actions 234 00:12:34,830 --> 00:12:37,550 and therefore middleware functions. 235 00:12:37,550 --> 00:12:41,340 And we will need that todo.model which we just worked on 236 00:12:41,340 --> 00:12:45,523 so we can require that from /models/todo.model. 237 00:12:47,730 --> 00:12:48,563 And then with that, 238 00:12:48,563 --> 00:12:51,320 then here, for example, for getting all the todos, 239 00:12:51,320 --> 00:12:56,320 what we can do is we can turn this into a async function 240 00:12:56,800 --> 00:13:01,800 so that we can get our todos by awaiting Todo.getAllTodos. 241 00:13:04,350 --> 00:13:07,420 And we might wanna put this into a try-catch block 242 00:13:07,420 --> 00:13:09,580 because, of course, since we're interacting 243 00:13:09,580 --> 00:13:10,930 with the database here, 244 00:13:10,930 --> 00:13:13,250 this could be failing, 245 00:13:13,250 --> 00:13:14,950 so I wanna catch errors 246 00:13:14,950 --> 00:13:18,113 and return next error here if we have an error. 247 00:13:19,403 --> 00:13:22,340 Otherwise, thereafter, I wanna use my todos. 248 00:13:22,340 --> 00:13:25,930 So, as always, I'll actually turn this into a variable 249 00:13:25,930 --> 00:13:28,440 so that we have the right scope. 250 00:13:28,440 --> 00:13:29,330 And then here, 251 00:13:29,330 --> 00:13:32,390 I can use the res object to call the json method 252 00:13:32,390 --> 00:13:35,263 to send back a response in the JSON format. 253 00:13:36,560 --> 00:13:39,130 And the data which I wanna send back here 254 00:13:39,130 --> 00:13:41,020 actually is my todos array, 255 00:13:41,020 --> 00:13:44,990 but I'll actually send back an object with a todos key 256 00:13:44,990 --> 00:13:47,520 which then holds this todos array. 257 00:13:47,520 --> 00:13:48,780 We could have also send back 258 00:13:48,780 --> 00:13:52,060 the todos array itself like this. 259 00:13:52,060 --> 00:13:53,180 This would also work 260 00:13:53,180 --> 00:13:56,640 because just an array is also valid JSON. 261 00:13:56,640 --> 00:13:58,890 But here I'll wrap it into an extra object 262 00:13:58,890 --> 00:14:02,863 and send back the array under a todos key in that object. 263 00:14:04,710 --> 00:14:06,660 And that should fetch us all the todos. 264 00:14:07,640 --> 00:14:09,240 Now, for adding a todo here, 265 00:14:09,240 --> 00:14:11,320 that's the next action I wanna work on, 266 00:14:11,320 --> 00:14:13,940 I, of course, need to get my todoText 267 00:14:13,940 --> 00:14:16,973 which I wanna get from req.body.text like this, 268 00:14:17,939 --> 00:14:21,775 assuming that the incoming request body will have 269 00:14:21,775 --> 00:14:22,858 a text field. 270 00:14:23,804 --> 00:14:25,193 So we'll have to make sure 271 00:14:25,193 --> 00:14:28,092 that when we send a request to our API later 272 00:14:28,092 --> 00:14:30,588 that this POST request has a request body 273 00:14:30,588 --> 00:14:33,310 with a text field inside of it. 274 00:14:33,310 --> 00:14:34,143 And then with that, 275 00:14:34,143 --> 00:14:38,050 we can, of course, create our todo with new Todo 276 00:14:38,050 --> 00:14:40,690 and pass the todoText to it. 277 00:14:40,690 --> 00:14:42,500 The second-parameter value, 278 00:14:42,500 --> 00:14:44,480 the id which we could also pass in, 279 00:14:44,480 --> 00:14:45,820 is not passed in 280 00:14:45,820 --> 00:14:48,870 because here we are creating a todo for the first time, 281 00:14:48,870 --> 00:14:51,033 and therefore, of course, we have no id. 282 00:14:52,360 --> 00:14:54,500 But with that, we got this todo, 283 00:14:54,500 --> 00:14:56,913 and now we can call todo.save here. 284 00:14:57,930 --> 00:14:59,690 This, of course, returns a promise, 285 00:14:59,690 --> 00:15:00,830 and therefore, as always, 286 00:15:00,830 --> 00:15:04,730 I'll turn this into async function and await this, 287 00:15:04,730 --> 00:15:08,110 and as always, wrap this into try-catch 288 00:15:08,110 --> 00:15:11,340 to catch any potential errors we might be facing 289 00:15:11,340 --> 00:15:14,070 so that we can actually let 290 00:15:14,070 --> 00:15:17,370 Express.js' default error-handler handle this 291 00:15:17,370 --> 00:15:19,763 if something goes wrong, like this. 292 00:15:21,530 --> 00:15:23,090 Now, if nothing goes wrong, 293 00:15:23,090 --> 00:15:25,380 if we make it past this try-catch block, 294 00:15:25,380 --> 00:15:27,590 then we did create a todo, 295 00:15:27,590 --> 00:15:30,400 and then I'll send back a JSON response 296 00:15:30,400 --> 00:15:33,410 because we always send back JSON responses 297 00:15:33,410 --> 00:15:34,990 when we build such an API. 298 00:15:34,990 --> 00:15:39,110 We never send back HTML, and we never redirect 299 00:15:39,110 --> 00:15:42,010 because we don't care about what the client does. 300 00:15:42,010 --> 00:15:44,240 We just exchange data, as you learned. 301 00:15:44,240 --> 00:15:49,010 And here in this object, I'll just add a message of saying 302 00:15:49,010 --> 00:15:52,950 Added todo successfully, or anything like this. 303 00:15:52,950 --> 00:15:57,480 And I'll add a second key-value pair to this response data, 304 00:15:57,480 --> 00:15:59,520 and that's the createdTodo 305 00:15:59,520 --> 00:16:03,540 where I pass back that todo here which was created. 306 00:16:03,540 --> 00:16:06,690 Or, actually, I'll not pass it back like this. 307 00:16:06,690 --> 00:16:10,740 Instead, on that todo, I wanna set the id field 308 00:16:10,740 --> 00:16:15,740 and set this equal to the id of the todo that was inserted. 309 00:16:16,570 --> 00:16:18,480 And for this, it is very convenient 310 00:16:18,480 --> 00:16:20,880 that in the todo.model in the save method, 311 00:16:20,880 --> 00:16:24,820 we return the promise that is yielded by insertOne, 312 00:16:24,820 --> 00:16:28,230 and it turns out that the promise yielded by insertOne 313 00:16:28,230 --> 00:16:30,500 eventually results to an object 314 00:16:30,500 --> 00:16:33,500 which holds the id that was inserted. 315 00:16:33,500 --> 00:16:36,480 So therefore, here in todos.controller, 316 00:16:36,480 --> 00:16:38,180 I get the result here 317 00:16:39,702 --> 00:16:41,540 of that operation, 318 00:16:41,540 --> 00:16:46,540 and then I can add a variable, insertedId for example, 319 00:16:46,890 --> 00:16:48,948 which I can get from that result. 320 00:16:48,948 --> 00:16:50,150 So insertedId is then equal to result.insertedId. 321 00:16:53,110 --> 00:16:55,760 This field will exist on this result object 322 00:16:55,760 --> 00:16:59,410 because this result object is generated by MongoDB, 323 00:16:59,410 --> 00:17:01,210 by this MongoDB package, 324 00:17:01,210 --> 00:17:05,290 and it will hold the id of the todo that was created. 325 00:17:05,290 --> 00:17:09,960 And then I'll set todo.id equal to insertedId.toString 326 00:17:09,960 --> 00:17:12,579 to force a conversion to a regular string 327 00:17:12,579 --> 00:17:14,583 instead of having this object id. 328 00:17:15,579 --> 00:17:18,010 And therefore now, this todo which I created here, 329 00:17:18,010 --> 00:17:20,210 which doesn't have an id initially, 330 00:17:20,210 --> 00:17:21,589 will now have an id 331 00:17:21,589 --> 00:17:25,680 because I set that id after I inserted it into the database, 332 00:17:25,680 --> 00:17:30,140 and therefore once I have that automatically created id, 333 00:17:30,140 --> 00:17:32,560 and therefore now it's this updated todo 334 00:17:32,560 --> 00:17:35,593 which now contains an id which I will return here. 335 00:17:38,060 --> 00:17:40,720 Now, let's ignore update and delete for now. 336 00:17:40,720 --> 00:17:43,610 These are two important controller actions already 337 00:17:43,610 --> 00:17:46,283 which allow us to create new todos and to get todos, 338 00:17:47,170 --> 00:17:50,750 and therefore now we wanna add routes for those actions 339 00:17:50,750 --> 00:17:54,313 and then also add one important middleware to app.js.