1 00:00:00,908 --> 00:00:04,770 -: (Memi) So let's talk about what is an API. 2 00:00:04,770 --> 00:00:06,030 As you probably remember, 3 00:00:06,030 --> 00:00:09,870 the title of this course is about REST API. 4 00:00:09,870 --> 00:00:12,240 So we'll talk about REST later. 5 00:00:12,240 --> 00:00:14,550 Let's begin with the API part. 6 00:00:14,550 --> 00:00:19,550 So API is an acronym of Application Programming Interface. 7 00:00:20,250 --> 00:00:22,470 Now if it doesn't make sense to you 8 00:00:22,470 --> 00:00:25,890 then let's look at the Wikipedia explanation of API. 9 00:00:25,890 --> 00:00:27,750 So according to Wikipedia 10 00:00:27,750 --> 00:00:31,680 an API is a set of clearly defined methods 11 00:00:31,680 --> 00:00:34,830 of communication among various components. 12 00:00:34,830 --> 00:00:37,080 Now notice that the components part 13 00:00:37,080 --> 00:00:41,700 in this explanation refers to software components. 14 00:00:41,700 --> 00:00:42,533 But first, 15 00:00:42,533 --> 00:00:45,333 let's talk about the interface part of the API. 16 00:00:46,230 --> 00:00:49,500 You're probably familiar with user interface. 17 00:00:49,500 --> 00:00:52,410 User interface is what you the user, 18 00:00:52,410 --> 00:00:54,900 sees when you look at something. 19 00:00:54,900 --> 00:00:56,220 In the case of websites, 20 00:00:56,220 --> 00:00:58,410 it's probably the homepage of the websites 21 00:00:58,410 --> 00:00:59,940 that you are browsing to. 22 00:00:59,940 --> 00:01:04,940 So interface is the part that is exposed to you the user. 23 00:01:05,040 --> 00:01:07,470 And the word exposed here is very, 24 00:01:07,470 --> 00:01:09,960 very important as we will see later. 25 00:01:09,960 --> 00:01:12,360 So this is a part that is exposed 26 00:01:12,360 --> 00:01:15,090 to you when you try to use something. 27 00:01:15,090 --> 00:01:18,150 And as an end user or as a human, 28 00:01:18,150 --> 00:01:21,720 the interface is a visual representation 29 00:01:21,720 --> 00:01:23,943 of the content that you are looking at. 30 00:01:25,350 --> 00:01:29,040 The same is also true for application interface. 31 00:01:29,040 --> 00:01:30,960 In application interface, 32 00:01:30,960 --> 00:01:35,700 the interface is the part that is exposed to an application 33 00:01:35,700 --> 00:01:37,560 not to an end user. 34 00:01:37,560 --> 00:01:38,820 And what you see right now 35 00:01:38,820 --> 00:01:42,120 on the screen is a specific kind of an API 36 00:01:42,120 --> 00:01:43,920 or an interface 37 00:01:43,920 --> 00:01:47,100 that is exposed by an application. 38 00:01:47,100 --> 00:01:48,870 Now you the end user, 39 00:01:48,870 --> 00:01:49,920 the human, 40 00:01:49,920 --> 00:01:53,430 you are not supposed to ever see this kind of API. 41 00:01:53,430 --> 00:01:54,570 It makes no sense. 42 00:01:54,570 --> 00:01:58,380 It has a lot of letters, a lot of numbers, some slashes, 43 00:01:58,380 --> 00:02:02,010 and it basically completely incomprehensible for humans. 44 00:02:02,010 --> 00:02:05,610 But application fully understands this. 45 00:02:05,610 --> 00:02:09,780 Now take a look at the first line of this API. 46 00:02:09,780 --> 00:02:12,210 This is the address of the API. 47 00:02:12,210 --> 00:02:15,420 This is the address of the interface that 48 00:02:15,420 --> 00:02:17,217 the application is going to use. 49 00:02:17,217 --> 00:02:20,340 And this is the main part we are going to deal with 50 00:02:20,340 --> 00:02:21,660 in this course. 51 00:02:21,660 --> 00:02:23,100 But again before, 52 00:02:23,100 --> 00:02:26,130 we are going to dive into the REST API, 53 00:02:26,130 --> 00:02:27,630 or into web API. 54 00:02:27,630 --> 00:02:30,540 Let's first understand what is the terminology 55 00:02:30,540 --> 00:02:33,780 that we are going to use when talking about API. 56 00:02:33,780 --> 00:02:35,160 So in this example, 57 00:02:35,160 --> 00:02:36,930 we have two softwares. 58 00:02:36,930 --> 00:02:39,270 We have users management software, 59 00:02:39,270 --> 00:02:41,730 and we have orders management software. 60 00:02:41,730 --> 00:02:43,350 And those two softwares, 61 00:02:43,350 --> 00:02:45,390 they want to communicate with each other. 62 00:02:45,390 --> 00:02:46,470 For example, 63 00:02:46,470 --> 00:02:50,460 the users software wants to access the orders software 64 00:02:50,460 --> 00:02:53,976 and ask it what are the orders that were made 65 00:02:53,976 --> 00:02:55,500 by a specific user. 66 00:02:55,500 --> 00:02:57,720 So in order to do that, 67 00:02:57,720 --> 00:03:01,260 the users software goes to the orders software. 68 00:03:01,260 --> 00:03:02,430 With this question. 69 00:03:02,430 --> 00:03:05,040 I want to get the users orders. 70 00:03:05,040 --> 00:03:09,865 Now how does the users software talk to the orders software? 71 00:03:09,865 --> 00:03:12,863 The order software publishes an API. 72 00:03:12,863 --> 00:03:17,040 The API is the thing that the users software can see 73 00:03:17,040 --> 00:03:20,430 and access and use it in order to get access 74 00:03:20,430 --> 00:03:24,270 to the internal data stored in the orders software. 75 00:03:24,270 --> 00:03:27,330 Now this kind of API publishing 76 00:03:27,330 --> 00:03:29,877 called exposing an API. 77 00:03:29,877 --> 00:03:34,410 The API is exposed by the orders management software 78 00:03:34,410 --> 00:03:37,170 and after it is exposed and becomes public 79 00:03:37,170 --> 00:03:41,073 then other software or other software components can use it.