1 00:00:01,470 --> 00:00:07,570 So another thing that you use go for quite regularly is to read and write from Jason. 2 00:00:07,650 --> 00:00:10,030 And if you're not familiar with Jason, don't worry about it. 3 00:00:10,050 --> 00:00:11,790 There's an example right here in front of you. 4 00:00:12,390 --> 00:00:16,500 Jason stands for Jason, as some people pronounce it. 5 00:00:16,910 --> 00:00:19,950 It stands for JavaScript object notation. 6 00:00:19,950 --> 00:00:27,060 And it's just a way of getting information from one place to another in a structured format and go makes 7 00:00:27,060 --> 00:00:29,530 it really, really easy to work with Jason. 8 00:00:29,700 --> 00:00:37,050 So typically, you would call some external service an API on some external service and you would receive 9 00:00:37,050 --> 00:00:41,180 from your call a response that consists of a file like this, Jason. 10 00:00:41,670 --> 00:00:47,940 So it's a structured format and this one actually starts and ends with square brackets. 11 00:00:47,950 --> 00:00:54,600 So this is what you might think of as an array or a number one or more entries that all have a similar 12 00:00:54,600 --> 00:00:55,020 format. 13 00:00:55,590 --> 00:00:57,450 So in this case, we have two people. 14 00:00:57,570 --> 00:00:59,280 We have one that's named Clark Kent. 15 00:00:59,820 --> 00:01:00,870 His first name is Clark. 16 00:01:00,870 --> 00:01:02,000 His last name is Kent. 17 00:01:02,010 --> 00:01:04,020 He has black hair and he has a dog. 18 00:01:04,620 --> 00:01:06,690 And the next one is Bruce Wayne. 19 00:01:06,930 --> 00:01:09,630 And he has black hair, but he doesn't have a dog. 20 00:01:09,630 --> 00:01:14,490 And I don't know if Bruce Wayne actually had a dog or not, but for the purposes of this exercise, 21 00:01:14,490 --> 00:01:15,150 he does not. 22 00:01:15,840 --> 00:01:21,180 So imagine, if you will, that you've called some external external service and you've received this 23 00:01:21,180 --> 00:01:27,930 response and you need to get it into a format that you can use because this is just a string and this 24 00:01:27,930 --> 00:01:29,990 is not something we can work with very easily. 25 00:01:30,000 --> 00:01:33,630 So one of the things we can do is actually define a type. 26 00:01:34,080 --> 00:01:37,170 So I'm going to define a type called person. 27 00:01:37,950 --> 00:01:44,100 And this is just my own data structure and it is a struct and it has a few members and the members in 28 00:01:44,130 --> 00:01:49,400 this type correspond to the entries in each one of these things in the adjacent file. 29 00:01:49,740 --> 00:01:55,050 So I'll call my first one first name and it's a string and then I'm going to put this special tag after 30 00:01:55,050 --> 00:01:55,200 it. 31 00:01:55,200 --> 00:02:02,700 And this will tell go that when you receive or you're creating Jasen in this format, here's what you 32 00:02:02,700 --> 00:02:12,090 use for the the name's Jason Colon, that in quotes first underscore name and this exactly matches what 33 00:02:12,090 --> 00:02:12,500 is here. 34 00:02:12,930 --> 00:02:14,670 So I'll do the same thing for last name. 35 00:02:17,620 --> 00:02:24,880 And again, the entry in Jason would be last underscore name and hair color. 36 00:02:27,760 --> 00:02:37,660 Jason Hare underscore Cullen and finally has dug, but this is not a string, this is a bull, Julian, 37 00:02:38,470 --> 00:02:41,710 and this is going to be has underscored dog. 38 00:02:42,130 --> 00:02:47,390 So now that I've defined this type, I can use that type to unmerciful. 39 00:02:47,410 --> 00:02:53,650 Jason, this Jason file, which we're pretending we got from an external API into a struct. 40 00:02:53,680 --> 00:03:01,240 So what we do, first of all, is we declare a variable and I'll call my variable unmuzzled and I'm 41 00:03:01,240 --> 00:03:08,850 calling it that because the functions used in the Jason package in Gollan are called Mercial and unmerciful. 42 00:03:08,890 --> 00:03:13,510 So this one is unmuzzled and it's going to be a type of slice person. 43 00:03:14,170 --> 00:03:20,740 And the reason it's a slice is because this Jason, in the format that it's presented here has one or 44 00:03:20,740 --> 00:03:21,550 more entries. 45 00:03:21,580 --> 00:03:22,180 Here's one. 46 00:03:22,180 --> 00:03:22,810 Here's two. 47 00:03:22,810 --> 00:03:23,800 It might only have one. 48 00:03:23,800 --> 00:03:24,790 It might have a thousand. 49 00:03:25,060 --> 00:03:31,390 But I'm creating a slice because I know that what I'm getting from my Jason might have more than one 50 00:03:31,390 --> 00:03:31,780 entry. 51 00:03:32,050 --> 00:03:37,780 So how do I get it out of Jason into my variable that I've just created called on Marshall? 52 00:03:37,900 --> 00:03:38,560 Well, it's quite easy. 53 00:03:39,100 --> 00:03:45,490 Error is assigned the value of Jason, and that's the package in the standard library. 54 00:03:45,820 --> 00:03:49,210 And I'm going to call the function on Marshall now. 55 00:03:49,210 --> 00:03:52,780 And Marshall, when we point out it, you see that it takes two parameters. 56 00:03:52,810 --> 00:03:55,160 One is a slice of bytes. 57 00:03:55,250 --> 00:03:58,150 Well, this is a string, so we need to convert that to a slice of bytes. 58 00:03:58,150 --> 00:03:59,330 But that easy, that's easy. 59 00:03:59,830 --> 00:04:06,070 And the second is an interface that you're going to put the contents of this slice of bytes into, and 60 00:04:06,070 --> 00:04:07,650 that will be our variable on martialled. 61 00:04:08,110 --> 00:04:10,900 So how do I convert from a string to a slice of bytes? 62 00:04:10,930 --> 00:04:11,610 Well, it's quite easy. 63 00:04:12,370 --> 00:04:13,600 Slice byte. 64 00:04:13,600 --> 00:04:17,440 And then in parentheses, the data that I want to convert to a slice of bytes. 65 00:04:17,440 --> 00:04:20,350 And in this case it's the variable called my JSON. 66 00:04:21,250 --> 00:04:22,780 And where do I want to put this? 67 00:04:22,870 --> 00:04:26,230 I want to put it into a reference to a commercial. 68 00:04:27,610 --> 00:04:28,810 Now we check for our error. 69 00:04:28,840 --> 00:04:40,030 If error is not equal to nil, then I shall just say log print line error, martialing Jason and then 70 00:04:40,030 --> 00:04:40,710 I'll print the error. 71 00:04:42,580 --> 00:04:43,010 All right. 72 00:04:43,030 --> 00:04:45,320 So once I have this, what can I do with it? 73 00:04:45,340 --> 00:04:46,390 Well, let's print it out. 74 00:04:46,390 --> 00:04:53,440 Log print F and I'm going to use the print F because I want to substitute something for a placeholder 75 00:04:53,440 --> 00:04:54,730 and I'll just put on martialled. 76 00:04:56,490 --> 00:05:03,840 Oops, I got to put that in quotation marks on martialled colon and then present the subject, putting 77 00:05:03,840 --> 00:05:07,920 an interface in there and what I want to put in there is my variable on martialed. 78 00:05:08,550 --> 00:05:08,910 All right. 79 00:05:08,940 --> 00:05:10,280 So let's see if we got this right. 80 00:05:10,290 --> 00:05:14,190 Let's run this go run may not go. 81 00:05:15,990 --> 00:05:18,270 And we have this value given back. 82 00:05:18,270 --> 00:05:20,310 And Marshall is Clark Kent Black. 83 00:05:20,310 --> 00:05:20,730 True. 84 00:05:20,910 --> 00:05:26,760 Bruce Wayne Black Fault's, which exactly corresponds to the entry in Jason in the Jason file. 85 00:05:27,090 --> 00:05:29,070 But now it's been converted to obstruct. 86 00:05:29,190 --> 00:05:30,110 So that's pretty easy. 87 00:05:30,540 --> 00:05:33,750 So we can read Jason into a struct. 88 00:05:34,020 --> 00:05:36,480 How do we write Jason from a struct. 89 00:05:36,540 --> 00:05:40,410 Well that's pretty easy to write, Jason. 90 00:05:40,410 --> 00:05:41,670 From a struct. 91 00:05:41,700 --> 00:05:43,050 Well, first of all, let's create a struct. 92 00:05:44,220 --> 00:05:48,680 So I will call the struct my slice and it's going to be a slice. 93 00:05:48,720 --> 00:05:53,500 Sorry, Daria, that again ver my slice is going to be a slice of person. 94 00:05:54,570 --> 00:05:56,040 And now let's put some values in there. 95 00:05:56,040 --> 00:06:05,460 So I'll say ver mercial, I'll call it meone just for Mercial me one and it's going to be a person and 96 00:06:05,460 --> 00:06:06,480 let's put some values in there. 97 00:06:06,480 --> 00:06:16,590 And one dot first name is equal to I don't know, we need another superhero Wally and one dot last name 98 00:06:17,910 --> 00:06:18,960 equals W. 99 00:06:21,610 --> 00:06:31,540 And one good hair color equals red and one has Doug equals false, I'm not sure if the Flash has a dog 100 00:06:31,540 --> 00:06:37,040 or not, but again, this is just the purpose of this exercise is just to show how things work. 101 00:06:37,060 --> 00:06:41,320 So my superhero knowledge may be somewhat limited and I apologize for that. 102 00:06:41,830 --> 00:06:45,160 Now I'm going to append this and one variable to this slice. 103 00:06:45,160 --> 00:06:47,640 So I'll put an entry into this slice and that's pretty easy. 104 00:06:47,980 --> 00:06:54,470 My slice equals append and I'm appending to my slice and I'm putting in the value add one. 105 00:06:55,120 --> 00:06:59,560 Now let's copy this whole thing and just change the variable names and the values. 106 00:06:59,560 --> 00:07:05,080 So we'll have to represent our slice of our M2 and I'll change these all to M2. 107 00:07:10,920 --> 00:07:13,050 And I'll change this to Diana. 108 00:07:14,850 --> 00:07:15,420 Prince. 109 00:07:17,730 --> 00:07:23,580 Black and she does not have a dog either, and now I'll put em to into this slice. 110 00:07:24,360 --> 00:07:30,090 So now I've created a slice that consists of two entries it has and one which is not called in, one 111 00:07:30,090 --> 00:07:33,750 in the slice, but it has an entry with Wally West and an entry with Diana Prince. 112 00:07:34,800 --> 00:07:41,850 So now I want to convert this into Jason and I'll create a variable called Jason and potentially an 113 00:07:41,850 --> 00:07:42,270 error. 114 00:07:42,720 --> 00:07:46,560 And that is a sign the value of and we call the Jason package again. 115 00:07:46,740 --> 00:07:48,480 And this time we want to Marshall. 116 00:07:48,510 --> 00:07:52,620 Now I'm going to use Marshall indent just because it makes it more readable. 117 00:07:52,860 --> 00:07:55,380 All that does is format our Jason nicely. 118 00:07:55,620 --> 00:07:59,730 If I just use Marshall, it wouldn't have any nice tabs or line breaks. 119 00:07:59,730 --> 00:08:02,500 It would make it really as small as it possibly could. 120 00:08:02,730 --> 00:08:09,450 So in production, when you're sending Jason, say, to a remote request, say you build an API that 121 00:08:09,960 --> 00:08:13,260 responds with Jason, you probably wouldn't use Marshall in debt. 122 00:08:13,260 --> 00:08:18,210 But for development purposes, when I want to look at the content that I'm producing, I always use 123 00:08:18,210 --> 00:08:18,960 Marshall in debt. 124 00:08:19,200 --> 00:08:21,950 So what are we martialing into Jason? 125 00:08:22,110 --> 00:08:26,370 We're marshaling my slice and it has no prefix. 126 00:08:26,370 --> 00:08:30,720 You can put a prefix in there if you want to, but you rarely do, or at least I rarely do. 127 00:08:30,720 --> 00:08:32,430 You might find situations where you have to. 128 00:08:32,520 --> 00:08:33,480 And how much do you want to win? 129 00:08:33,660 --> 00:08:35,220 It's identity, a few spaces. 130 00:08:36,150 --> 00:08:39,330 So we've called that we should check for our error. 131 00:08:39,360 --> 00:08:46,170 If error is not equal to nil, then I will log print line error martialing. 132 00:08:51,790 --> 00:08:56,210 And I'll just put the air in there, otherwise I want to print this out. 133 00:08:56,410 --> 00:08:58,740 Now, what does Jason Marshall intent give us? 134 00:08:59,200 --> 00:09:04,750 It hands back a slice of bytes and potentially an error so I could just write the slice of bytes, but 135 00:09:04,750 --> 00:09:05,980 that would not be very useful. 136 00:09:05,980 --> 00:09:07,880 You wouldn't get much useful information from that. 137 00:09:08,170 --> 00:09:17,560 So instead, let's just use our format, package format or print F or format print, and we'll convert 138 00:09:17,560 --> 00:09:23,200 our slice of bytes into a string by saying String and new Jason. 139 00:09:24,250 --> 00:09:26,360 All right, let's try this out and see how it works. 140 00:09:26,360 --> 00:09:27,430 So I'll clear the screen. 141 00:09:31,070 --> 00:09:33,590 And I'll make this a little bit bigger so I can see what's going on. 142 00:09:35,850 --> 00:09:39,720 Let's run this go, run, mean, go. 143 00:09:42,610 --> 00:09:49,510 So first of all, I get the content from the first part of our program where it actually creates a struct 144 00:09:49,510 --> 00:09:50,860 from Jason, there it is. 145 00:09:51,160 --> 00:09:55,930 And then it outputs my JSON that I constructed as a slice of struct. 146 00:09:56,470 --> 00:09:58,990 It outputs it as Jason, and that's all there is to it. 147 00:09:59,290 --> 00:10:05,200 Now, this presupposes that, you know, the format of the JSON that you're receiving, if you're receiving 148 00:10:05,200 --> 00:10:08,650 JSON, if you don't know the format, there's a way to handle that. 149 00:10:08,650 --> 00:10:10,390 But I'm not going to cover that in this lecture. 150 00:10:10,390 --> 00:10:13,570 If we run into that situation later in the course, we will cover it. 151 00:10:14,860 --> 00:10:19,660 But in the most cases, it's it's always best if you know the structure of the duration you're going 152 00:10:19,660 --> 00:10:22,270 to be receiving, just write a struct. 153 00:10:22,270 --> 00:10:26,140 The conforms to that structure and it will make your life ever so much easier. 154 00:10:26,530 --> 00:10:26,860 All right. 155 00:10:26,860 --> 00:10:28,280 That's enough for this time around. 156 00:10:28,300 --> 00:10:28,990 Let's move on.