1 00:00:00,305 --> 00:00:01,808 - [Instructor] Hi and welcome back to the course. 2 00:00:01,808 --> 00:00:04,342 In the last video, we did request parsing, 3 00:00:04,342 --> 00:00:07,269 and we made sure that we could only pass certain fields 4 00:00:07,269 --> 00:00:10,334 through our JSON payload to our endpoints. 5 00:00:10,334 --> 00:00:12,249 I also suggested that you try to do 6 00:00:12,249 --> 00:00:14,409 the same thing for the POST method, 7 00:00:14,409 --> 00:00:17,265 so let's do that just now. 8 00:00:17,265 --> 00:00:21,432 I'm just going to copy, and then I'm going to paste, 9 00:00:22,293 --> 00:00:26,032 then I'm going to remove the data from here. 10 00:00:26,032 --> 00:00:29,449 Now, what was wrong with what I just did? 11 00:00:32,578 --> 00:00:35,628 Hopefully, you acknowledged that it is wrong, 12 00:00:35,628 --> 00:00:39,562 normally at least, often, to copy and paste. 13 00:00:39,562 --> 00:00:42,537 I essentially copied and pasted and didn't change 14 00:00:42,537 --> 00:00:46,456 anything at all, which means that this thing here 15 00:00:46,456 --> 00:00:48,622 is the same as this thing here, 16 00:00:48,622 --> 00:00:51,106 and there is probably a way of making sure 17 00:00:51,106 --> 00:00:52,772 that they are not duplicated. 18 00:00:52,772 --> 00:00:54,883 So why do we not want to duplicate them? 19 00:00:54,883 --> 00:00:58,259 For example, say we want to change the help message, 20 00:00:58,259 --> 00:01:03,057 we now have to change it in line 26, and also in line 47, 21 00:01:03,057 --> 00:01:04,870 and if we forget to change one of them, 22 00:01:04,870 --> 00:01:06,062 they're going to be out of sync, 23 00:01:06,062 --> 00:01:06,941 and then that's going to result 24 00:01:06,941 --> 00:01:09,597 in poor user experience and so on. 25 00:01:09,597 --> 00:01:12,728 Another example, we want to add a new argument 26 00:01:12,728 --> 00:01:16,365 to the parser, so now we have to add a new argument up here, 27 00:01:16,365 --> 00:01:18,279 and then another one down here. 28 00:01:18,279 --> 00:01:21,170 Overall, just not very nice. 29 00:01:21,170 --> 00:01:25,961 So what I'm gonna do, is I'm going to remove this, 30 00:01:25,961 --> 00:01:29,952 and I'm going to cut this, and then we're gonna 31 00:01:29,952 --> 00:01:31,535 put it in the item. 32 00:01:33,115 --> 00:01:37,166 So now the parser is going to belong to the item class 33 00:01:37,166 --> 00:01:41,799 as opposed to belonging in one of the methods, 34 00:01:41,799 --> 00:01:45,293 but notice there is no self in front, 35 00:01:45,293 --> 00:01:48,330 so the parser belongs to the class itself, 36 00:01:48,330 --> 00:01:51,631 and not to one specific item resource, 37 00:01:51,631 --> 00:01:54,106 so the way to call and use this parser 38 00:01:54,106 --> 00:01:57,833 is by saying Item.parser.parse_args. 39 00:01:57,833 --> 00:01:59,642 Remember the I has to be upper case 40 00:01:59,642 --> 00:02:02,258 just as it is in the class, 41 00:02:02,258 --> 00:02:05,069 and similarly down here in the PUT method, 42 00:02:05,069 --> 00:02:08,069 it should be Item.parser.parse_args. 43 00:02:09,077 --> 00:02:10,819 and that just makes things a lot nicer, 44 00:02:10,819 --> 00:02:12,451 and also a lot easier to reuse 45 00:02:12,451 --> 00:02:13,933 because now if we want to use 46 00:02:13,933 --> 00:02:16,558 this in another method, we just have to do this, 47 00:02:16,558 --> 00:02:18,475 and it's really simple. 48 00:02:19,608 --> 00:02:23,116 As an aside, I'll also mention why this data 49 00:02:23,116 --> 00:02:27,283 is up here, or rather why this data used to be down here. 50 00:02:30,271 --> 00:02:31,845 This data used to be down here, 51 00:02:31,845 --> 00:02:36,012 and it should be down here because of the following. 52 00:02:37,243 --> 00:02:41,298 The first thing we do is we filter out things, 53 00:02:41,298 --> 00:02:45,544 so we're saying if the name is already in our database, 54 00:02:45,544 --> 00:02:47,528 we don't want to do anything. 55 00:02:47,528 --> 00:02:50,312 This is an error first approach. 56 00:02:50,312 --> 00:02:52,480 The first thing we do is we look for errors, 57 00:02:52,480 --> 00:02:56,397 and if any errors happen, we stop and we break, 58 00:02:57,313 --> 00:03:00,249 and once all of the errors have been cleared, 59 00:03:00,249 --> 00:03:02,152 we start doing what we want to do. 60 00:03:02,152 --> 00:03:04,520 So the first thing we do is we deal with errors, 61 00:03:04,520 --> 00:03:06,247 and then we do what we want to do, 62 00:03:06,247 --> 00:03:09,364 and that way, we know that there are no errors 63 00:03:09,364 --> 00:03:12,168 that could happen in this piece of code here 64 00:03:12,168 --> 00:03:15,516 because we've already dealt with them before, 65 00:03:15,516 --> 00:03:19,341 and because here we are stopping if the name 66 00:03:19,341 --> 00:03:22,547 is already in the database, it doesn't make sense 67 00:03:22,547 --> 00:03:25,540 to load the data before it. 68 00:03:25,540 --> 00:03:29,379 Here we'd be loading data, and then we would be stopping 69 00:03:29,379 --> 00:03:33,546 if the item already exists, and we would never use the data, 70 00:03:34,405 --> 00:03:37,888 so that seems a bit wasteful, which is why 71 00:03:37,888 --> 00:03:40,159 the data was originally down here. 72 00:03:40,159 --> 00:03:41,411 The first thing we do is we make sure 73 00:03:41,411 --> 00:03:45,088 that we are okay to proceed, and then we actually proceed, 74 00:03:45,088 --> 00:03:48,427 and do the stuff that we want to do. 75 00:03:48,427 --> 00:03:49,799 Now okay, that's it for this video, 76 00:03:49,799 --> 00:03:51,232 so hopefully you learned something, 77 00:03:51,232 --> 00:03:53,090 and I'll see you in the very next one.