1 00:00:00,550 --> 00:00:02,119 - [Narrator] Hi and welcome back to the course. 2 00:00:02,119 --> 00:00:06,090 In this video we're going to look at deleting an item. 3 00:00:06,090 --> 00:00:08,198 We've gone through the most complex part of this app, 4 00:00:08,198 --> 00:00:09,741 which was authentication. 5 00:00:09,741 --> 00:00:11,821 And now we're just gonna be adding a few more end points 6 00:00:11,821 --> 00:00:13,583 to make sure that everything sticks together 7 00:00:13,583 --> 00:00:15,500 and then we'll be done. 8 00:00:16,841 --> 00:00:21,791 To add deletion of items, you know that the http verb 9 00:00:21,791 --> 00:00:25,810 is delete, so you can probably guess what the method 10 00:00:25,810 --> 00:00:27,060 is going to be. 11 00:00:31,267 --> 00:00:33,975 And then because this is inside the item resource, 12 00:00:33,975 --> 00:00:36,345 this has to have a name as well, 13 00:00:36,345 --> 00:00:39,409 and that is what we're going to be deleting. 14 00:00:39,409 --> 00:00:40,242 Okay. 15 00:00:41,615 --> 00:00:43,897 Now, what's going to happen now is a bit of 16 00:00:43,897 --> 00:00:46,897 an interesting Python sort of event, 17 00:00:49,201 --> 00:00:51,338 that happens very often and it's a very bad 18 00:00:51,338 --> 00:00:52,948 problem to debug. 19 00:00:52,948 --> 00:00:54,695 And it's the following. 20 00:00:54,695 --> 00:00:58,278 We're gonna say that items, our items list, 21 00:00:59,835 --> 00:01:03,835 is a list of the result of filtering on a lambda 22 00:01:05,992 --> 00:01:10,159 where the name is not equal to the name that was passed in. 23 00:01:13,426 --> 00:01:14,259 Okay. 24 00:01:15,511 --> 00:01:17,777 So, before we were doing this filtering, 25 00:01:17,777 --> 00:01:20,267 just like that, but we were looking for one specific 26 00:01:20,267 --> 00:01:23,015 element, now we're looking for all the elements 27 00:01:23,015 --> 00:01:25,096 except one, and that one 28 00:01:25,096 --> 00:01:26,871 is the one that's going to get deleted. 29 00:01:26,871 --> 00:01:28,358 So what we're gonna do essentially is 30 00:01:28,358 --> 00:01:32,108 overwrite our items list with a new list that 31 00:01:33,039 --> 00:01:37,206 is all of the elements except the one that was deleted. 32 00:01:40,408 --> 00:01:43,487 Do you spot any errors here? 33 00:01:43,487 --> 00:01:47,237 Anything that you think might cause an error? 34 00:01:50,106 --> 00:01:52,648 And to be fair, at first I didn't either. 35 00:01:52,648 --> 00:01:54,815 But Python is quite funny. 36 00:01:57,497 --> 00:02:00,334 Items is being used here, so what's gonna happen 37 00:02:00,334 --> 00:02:04,002 is that we're gonna filter and we're gonna use the 38 00:02:04,002 --> 00:02:06,085 items variable to filter. 39 00:02:07,966 --> 00:02:10,985 However, Python's gonna think that the items variable 40 00:02:10,985 --> 00:02:13,110 is only defined here, 41 00:02:13,110 --> 00:02:15,653 so it cannot possibly use the variable 42 00:02:15,653 --> 00:02:17,771 before it has been defined. 43 00:02:17,771 --> 00:02:20,418 Python's gonna think that we're using the variable's value 44 00:02:20,418 --> 00:02:22,997 to define the variable's value. 45 00:02:22,997 --> 00:02:24,671 And that's kinda like defining a word 46 00:02:24,671 --> 00:02:27,599 using the same word that you're trying to define. 47 00:02:27,599 --> 00:02:29,182 You cannot do that. 48 00:02:30,038 --> 00:02:32,794 And that happens because we've called this variable here 49 00:02:32,794 --> 00:02:34,961 items, so it's gonna think 50 00:02:35,917 --> 00:02:38,450 that we're creating a new variable items, 51 00:02:38,450 --> 00:02:41,647 that is only going to exist inside this method. 52 00:02:41,647 --> 00:02:44,480 This is gonna be a local variable. 53 00:02:45,377 --> 00:02:46,643 That's normally what happens. 54 00:02:46,643 --> 00:02:47,983 When you create a variable, that variable 55 00:02:47,983 --> 00:02:51,731 is a local variable that only exists in the method 56 00:02:51,731 --> 00:02:54,710 or the block that you created. 57 00:02:54,710 --> 00:02:56,655 However we don't wanna use that variable, 58 00:02:56,655 --> 00:03:00,309 we wanna use the global items variable. 59 00:03:00,309 --> 00:03:02,085 So then we just have to do that. 60 00:03:02,085 --> 00:03:04,347 See global items, and what that does, 61 00:03:04,347 --> 00:03:07,007 is it says, the items variable in this block 62 00:03:07,007 --> 00:03:09,340 is the outer items variable. 63 00:03:10,793 --> 00:03:11,985 Okay? 64 00:03:11,985 --> 00:03:13,946 Saved you a lot of pain there. 65 00:03:13,946 --> 00:03:18,113 And then what we're gonna do is say return item deleted. 66 00:03:21,967 --> 00:03:23,392 And that's it really. 67 00:03:23,392 --> 00:03:25,339 That is going to delete the item, 68 00:03:25,339 --> 00:03:27,685 because it's going to change the data base into 69 00:03:27,685 --> 00:03:29,935 not have that item anymore. 70 00:03:31,285 --> 00:03:34,903 Now, we could go into Postman and give it a go. 71 00:03:34,903 --> 00:03:37,208 And remember that when we change the app, 72 00:03:37,208 --> 00:03:41,519 and the app restarts, or we hand restart it, 73 00:03:41,519 --> 00:03:43,147 but it restarts on its own anyway. 74 00:03:43,147 --> 00:03:44,965 So none of the items are gonna be there. 75 00:03:44,965 --> 00:03:46,466 We can get the items, and you can see 76 00:03:46,466 --> 00:03:48,718 it's empty, so what we're gonna do 77 00:03:48,718 --> 00:03:52,247 is we're gonna post a new item, a new piano, 78 00:03:52,247 --> 00:03:55,441 and that creates the piano and then we can get 79 00:03:55,441 --> 00:03:57,474 our list of items and there you can see 80 00:03:57,474 --> 00:03:59,734 the piano is in there and the last thing we're going to do 81 00:03:59,734 --> 00:04:03,901 to verify that everything works is we're going to delete it. 82 00:04:05,352 --> 00:04:06,218 Okay? 83 00:04:06,218 --> 00:04:08,031 So what do you think is gonna happen when we press send? 84 00:04:08,031 --> 00:04:09,864 What's gonna come out? 85 00:04:12,287 --> 00:04:15,697 And you're correct, the message item deleted comes out. 86 00:04:15,697 --> 00:04:17,805 We have no proof when it has been deleted, 87 00:04:17,805 --> 00:04:21,025 but we have to trust that it has been deleted 88 00:04:21,025 --> 00:04:25,418 but we can still call the get items end point to verify 89 00:04:25,418 --> 00:04:28,517 and you can see that it's no longer there. 90 00:04:28,517 --> 00:04:29,977 So that's everything for this video. 91 00:04:29,977 --> 00:04:32,058 We've managed to delete an item, 92 00:04:32,058 --> 00:04:33,556 and I'll see you on the very next one.