1 00:00:02,020 --> 00:00:03,150 Now in this lecture, 2 00:00:03,150 --> 00:00:05,490 let me briefly come back to the question 3 00:00:05,490 --> 00:00:09,040 when you should build an API or a web service, 4 00:00:09,040 --> 00:00:11,210 and I'll use these terms interchangeably here 5 00:00:11,210 --> 00:00:14,170 because when I say API here in this lecture, 6 00:00:14,170 --> 00:00:17,290 I mean a URL-based API. 7 00:00:17,290 --> 00:00:21,489 So in the end, the web service where we expose various URLs 8 00:00:21,489 --> 00:00:24,830 to which other developers, other people can send requests 9 00:00:24,830 --> 00:00:27,550 and where the main goal of these URLs 10 00:00:27,550 --> 00:00:31,220 is to then return data, not HTML pages. 11 00:00:31,220 --> 00:00:33,540 Of course, you probably already have an idea 12 00:00:33,540 --> 00:00:36,670 of when you might wanna build such an API. 13 00:00:36,670 --> 00:00:40,020 For example, if you're building an alternative to Stripe, 14 00:00:40,020 --> 00:00:42,030 if you're building your own payment service 15 00:00:42,030 --> 00:00:44,570 and you wanna expose that to the world, 16 00:00:44,570 --> 00:00:48,040 but there also are other reasons and to understand those, 17 00:00:48,040 --> 00:00:49,720 let's take a step back 18 00:00:49,720 --> 00:00:53,050 and let's understand when a classic website 19 00:00:53,050 --> 00:00:54,840 makes most sense. 20 00:00:54,840 --> 00:00:56,610 So a website as we built it 21 00:00:56,610 --> 00:00:59,010 multiple times throughout this course 22 00:00:59,010 --> 00:01:01,750 where you have your views on the backend 23 00:01:01,750 --> 00:01:05,150 and where it's all about returning HTML code 24 00:01:05,150 --> 00:01:07,127 to the requester because the requester 25 00:01:07,127 --> 00:01:10,200 typically is the browser where a user, 26 00:01:10,200 --> 00:01:11,710 a visitor of your site, 27 00:01:11,710 --> 00:01:14,463 entered some URL or clicked some link. 28 00:01:15,470 --> 00:01:17,660 Now, such a website makes a lot of sense 29 00:01:17,660 --> 00:01:21,460 if you want people to, well, view your website 30 00:01:21,460 --> 00:01:24,960 and when your main product is the website itself. 31 00:01:24,960 --> 00:01:28,430 So for example, if you're building a blog or an online shop, 32 00:01:28,430 --> 00:01:32,150 then of course your website is the main product. 33 00:01:32,150 --> 00:01:34,940 The online shop we built before in this course 34 00:01:34,940 --> 00:01:36,800 is the product itself. 35 00:01:36,800 --> 00:01:39,770 We would earn money by having that shop 36 00:01:39,770 --> 00:01:42,560 where people can then buy something. 37 00:01:42,560 --> 00:01:43,480 So in such a case, 38 00:01:43,480 --> 00:01:46,460 such a traditional website makes a lot of sense 39 00:01:46,460 --> 00:01:50,790 because we have this tight coupling of frontend and backend, 40 00:01:50,790 --> 00:01:53,640 and we wanna render those dynamic pages, 41 00:01:53,640 --> 00:01:55,350 which contain our products 42 00:01:55,350 --> 00:01:59,253 or some user-specific data like cart and so on. 43 00:02:00,400 --> 00:02:04,010 Now, when it comes to building a web API or web service, 44 00:02:04,010 --> 00:02:05,810 then of course we have the case 45 00:02:05,810 --> 00:02:08,539 that we wanna build something like Stripe. 46 00:02:08,539 --> 00:02:10,520 Let's say Stripe doesn't exist yet 47 00:02:10,520 --> 00:02:13,630 and we have the idea that such a service, 48 00:02:13,630 --> 00:02:15,100 which other people can use, 49 00:02:15,100 --> 00:02:19,080 where we help them handle payments would be a great idea. 50 00:02:19,080 --> 00:02:21,510 We could then build such a service. 51 00:02:21,510 --> 00:02:24,010 But there also is an alternative use case 52 00:02:24,010 --> 00:02:26,490 which we haven't explored thus far 53 00:02:26,490 --> 00:02:30,620 and that use case would be that we mostly wanna expose 54 00:02:30,620 --> 00:02:33,030 some data in the end, 55 00:02:33,030 --> 00:02:36,750 some data that can then be consumed from different clients 56 00:02:36,750 --> 00:02:38,760 and I'll come back to this. 57 00:02:38,760 --> 00:02:40,370 Now, the left case here, 58 00:02:40,370 --> 00:02:43,240 building a web service like Stripe should be clear. 59 00:02:43,240 --> 00:02:46,570 We have the goal of giving our developers, 60 00:02:46,570 --> 00:02:49,170 customers access to this API. 61 00:02:49,170 --> 00:02:51,440 Probably we will charge them for that, 62 00:02:51,440 --> 00:02:53,890 but then they can use our service or API 63 00:02:53,890 --> 00:02:55,990 to integrate it into their own products, 64 00:02:55,990 --> 00:02:58,223 into their own sites or APIs. 65 00:02:59,150 --> 00:03:02,570 Of course, we could also use such a service on our own. 66 00:03:02,570 --> 00:03:06,450 If we are Stripe, we could use our ourselves, 67 00:03:06,450 --> 00:03:10,020 we could use our own service in some other product 68 00:03:10,020 --> 00:03:12,130 which might need payments 69 00:03:12,130 --> 00:03:15,160 to offer some other service to end customers. 70 00:03:15,160 --> 00:03:16,800 This, of course, would be possible. 71 00:03:16,800 --> 00:03:20,910 We can become a customer of ourselves in this case, 72 00:03:20,910 --> 00:03:22,693 probably without paying though. 73 00:03:23,790 --> 00:03:26,200 Now, the right case is interesting though. 74 00:03:26,200 --> 00:03:28,900 Of course, the borders are always kind of blurry, 75 00:03:28,900 --> 00:03:30,790 but we could be building an API, 76 00:03:30,790 --> 00:03:33,910 as we will do it throughout this course section, 77 00:03:33,910 --> 00:03:36,760 where we don't necessarily offer a service 78 00:03:36,760 --> 00:03:40,120 that is super useful to a lot of other developers. 79 00:03:40,120 --> 00:03:43,490 Instead, we could build an API which offers, for example, 80 00:03:43,490 --> 00:03:48,040 all these CRUD operations, create, read, update, and delete, 81 00:03:48,040 --> 00:03:51,250 for managing to-do's or anything like this. 82 00:03:51,250 --> 00:03:54,060 And then we could plan to use this ourselves, 83 00:03:54,060 --> 00:03:57,750 but we might have different user-facing clients 84 00:03:57,750 --> 00:04:00,490 that should be connected to this API. 85 00:04:00,490 --> 00:04:05,120 And with user-facing clients, I mean things like browsers, 86 00:04:05,120 --> 00:04:07,910 so a decoupled web frontend let's say, 87 00:04:07,910 --> 00:04:11,490 so a static page in the end with no backend code 88 00:04:11,490 --> 00:04:13,700 that might run on a different server, 89 00:04:13,700 --> 00:04:16,660 but which uses Ajax to talk to our API, 90 00:04:16,660 --> 00:04:19,820 to fetch data, send data and so on, 91 00:04:19,820 --> 00:04:21,279 but also other clients, 92 00:04:21,279 --> 00:04:24,083 like for example desktop or mobile apps. 93 00:04:25,070 --> 00:04:27,990 Of course, we could be building a mobile app, 94 00:04:27,990 --> 00:04:32,310 which lets users manage their daily to do's let's say, 95 00:04:32,310 --> 00:04:37,280 and that mobile app would need to talk to some server 96 00:04:37,280 --> 00:04:39,590 because we might not wanna store those to-do's 97 00:04:39,590 --> 00:04:41,560 just on the user's device. 98 00:04:41,560 --> 00:04:43,210 If the user switches the device, 99 00:04:43,210 --> 00:04:45,030 all the to-do's would be gone. 100 00:04:45,030 --> 00:04:47,090 We might wanna store them on our server 101 00:04:47,090 --> 00:04:48,723 and our database instead. 102 00:04:49,630 --> 00:04:52,610 Therefore, we need a server and we need a database, 103 00:04:52,610 --> 00:04:57,060 but what we don't need in that case is HTML code and views. 104 00:04:57,060 --> 00:04:59,150 Because if we're building a mobile app, 105 00:04:59,150 --> 00:05:01,480 it turns out that those mobile apps 106 00:05:01,480 --> 00:05:03,990 don't want HTML responses. 107 00:05:03,990 --> 00:05:06,410 Instead, there you build the user interface 108 00:05:06,410 --> 00:05:08,913 with totally different programming languages. 109 00:05:10,310 --> 00:05:12,890 There is a reason why there are dedicated courses 110 00:05:12,890 --> 00:05:15,390 teaching you mobile app development. 111 00:05:15,390 --> 00:05:18,470 You build user interfaces with other tools there 112 00:05:18,470 --> 00:05:23,113 with other languages, not necessarily with HTML and so on. 113 00:05:24,470 --> 00:05:27,140 Therefore, such a mobile app might want the data, 114 00:05:27,140 --> 00:05:30,530 but not the views, not the HTML code. 115 00:05:30,530 --> 00:05:32,780 And that would be another use case. 116 00:05:32,780 --> 00:05:36,110 We might not be building a service that's super useful 117 00:05:36,110 --> 00:05:38,110 to a lot of other people in the world, 118 00:05:38,110 --> 00:05:40,680 to a lot of other companies that should use it, 119 00:05:40,680 --> 00:05:42,770 but instead we might be building an API 120 00:05:42,770 --> 00:05:46,010 that's pretty much only useful to ourselves, 121 00:05:46,010 --> 00:05:48,970 but we don't plan on just building a website. 122 00:05:48,970 --> 00:05:51,350 Instead, we might wanna build such a mobile app 123 00:05:51,350 --> 00:05:53,900 and therefore we don't need the frontend part. 124 00:05:53,900 --> 00:05:55,410 We don't need the views. 125 00:05:55,410 --> 00:05:58,970 We just want an API to which our mobile app can talk 126 00:05:58,970 --> 00:06:01,130 so that it can fetch data from there 127 00:06:01,130 --> 00:06:05,100 and then display it in its native user interface. 128 00:06:05,100 --> 00:06:07,540 And this is also a common use case 129 00:06:07,540 --> 00:06:09,790 that you need a backend, but not a frontend, 130 00:06:09,790 --> 00:06:12,610 because your frontend might not be a website, 131 00:06:12,610 --> 00:06:15,393 but instead a mobile app or desktop app. 132 00:06:16,370 --> 00:06:18,920 Now still, it could also be a frontend. 133 00:06:18,920 --> 00:06:21,130 It would also be very common 134 00:06:21,130 --> 00:06:23,370 that you have different clients, 135 00:06:23,370 --> 00:06:27,750 let's say browsers and mobile apps talking to the same API 136 00:06:27,750 --> 00:06:31,620 because you might wanna have users on mobile devices 137 00:06:31,620 --> 00:06:35,090 and users who visit your website through a browser. 138 00:06:35,090 --> 00:06:36,960 This is also quite common. 139 00:06:36,960 --> 00:06:40,130 If you think about Facebook or Google Maps 140 00:06:40,130 --> 00:06:44,780 or basically any big company, you can visit their offerings, 141 00:06:44,780 --> 00:06:47,340 you can visit Facebook through the browser 142 00:06:47,340 --> 00:06:49,030 on your desktop device 143 00:06:49,030 --> 00:06:52,000 or you can visit it through their mobile app. 144 00:06:52,000 --> 00:06:55,940 And there, it is the case that the frontend on the browser 145 00:06:55,940 --> 00:06:57,230 and the mobile app, 146 00:06:57,230 --> 00:07:00,700 that these two are two totally different clients in the end, 147 00:07:00,700 --> 00:07:04,600 but they probably talk to the same Facebook API 148 00:07:04,600 --> 00:07:07,173 somewhere on some Facebook servers. 149 00:07:08,240 --> 00:07:10,000 So that's also a use case. 150 00:07:10,000 --> 00:07:11,900 And with this course section 151 00:07:11,900 --> 00:07:14,670 and the overall knowledge you gained throughout this course, 152 00:07:14,670 --> 00:07:17,700 you will be able to handle all these scenarios 153 00:07:17,700 --> 00:07:20,090 and all these use cases. 154 00:07:20,090 --> 00:07:21,840 So therefore, that was a lot of talking, 155 00:07:21,840 --> 00:07:23,180 but now it's hopefully clear 156 00:07:23,180 --> 00:07:25,280 why you might wanna build such APIs 157 00:07:25,280 --> 00:07:28,300 and what possible use cases are. 158 00:07:28,300 --> 00:07:30,110 Now, we're going to see this right case, 159 00:07:30,110 --> 00:07:33,920 this data API case in action throughout this course section, 160 00:07:33,920 --> 00:07:35,850 and therefore let's not waste any time 161 00:07:35,850 --> 00:07:37,293 and instead dive right in.