1 00:00:00,880 --> 00:00:05,960 So so far, we've figured out how to create variables, how to create our own types for variables. 2 00:00:06,280 --> 00:00:08,220 We had a brief introduction to pointers. 3 00:00:08,230 --> 00:00:09,520 We know what a struct is. 4 00:00:09,790 --> 00:00:13,570 We have a couple of other data structures, including maps and slices. 5 00:00:14,020 --> 00:00:19,630 Now it's time to look at looping, at going or changing over things. 6 00:00:19,960 --> 00:00:21,710 And again, it's not that difficult. 7 00:00:22,510 --> 00:00:24,150 So let's start with a for loop. 8 00:00:24,160 --> 00:00:28,780 And if you're coming from another programming language, you might be used to multiple kinds of loops. 9 00:00:28,780 --> 00:00:36,340 For example, a for loop a while loop, a do while loop, whatever it may be, go strives for simplicity. 10 00:00:36,550 --> 00:00:42,520 So it has one looping type the for loop because you can do anything you can do in a while, loop with 11 00:00:42,520 --> 00:00:44,340 a for loop and we'll get to that eventually. 12 00:00:44,350 --> 00:00:46,030 But right now let's have a look at a for loop. 13 00:00:47,080 --> 00:00:53,050 So I've cleared out all the code from my mindo go file and all I have left is an empty main main function 14 00:00:53,050 --> 00:00:54,220 and a package declaration. 15 00:00:54,230 --> 00:01:00,670 So let's create a loop and you create a for loop with the word not surprisingly for and you need to 16 00:01:00,670 --> 00:01:01,930 give it a place to start with. 17 00:01:01,930 --> 00:01:05,250 And what we're going to start at is zero. 18 00:01:05,260 --> 00:01:10,090 So we'll create a variable I and we will assign the value of zero to it. 19 00:01:10,300 --> 00:01:12,700 Then a semicolon which you almost never see and go. 20 00:01:12,700 --> 00:01:13,270 But there it is. 21 00:01:13,270 --> 00:01:16,170 We have one, then we have our condition. 22 00:01:16,180 --> 00:01:17,860 When do we want this loop to stop? 23 00:01:17,860 --> 00:01:24,600 And I will say stop this loop when I is less than or keep it going when I is less than or equal to ten. 24 00:01:25,300 --> 00:01:29,830 So once you get to 11, stop executing and then we have. 25 00:01:29,830 --> 00:01:30,940 What do we do with our counter. 26 00:01:30,940 --> 00:01:38,830 Our counter is EI plus plus which is just a shorthand that says the same thing as I equals I plus one 27 00:01:38,920 --> 00:01:44,620 and then I have curly braces and in between those curly braces is everything I want to do in this for 28 00:01:44,620 --> 00:01:48,340 loop, what I want to do, what we'll do, what we've been doing right along, we'll just print the 29 00:01:48,340 --> 00:01:55,330 terminal log print line and I'll just print the value of it so it automatically imported log for me. 30 00:01:55,870 --> 00:01:57,340 And this is my program. 31 00:01:57,350 --> 00:02:00,310 So what's it going to do while the program starts? 32 00:02:00,310 --> 00:02:02,190 It finds the main package easy. 33 00:02:02,200 --> 00:02:07,690 There's only one package and then it says execute whatever you find in the main function and we're going 34 00:02:07,690 --> 00:02:08,710 to execute a for loop. 35 00:02:08,710 --> 00:02:11,680 And what that for loop does is it initialize is a variable. 36 00:02:11,680 --> 00:02:18,640 I with the value of zero every time it goes for the loop, it adds one to I and it stops when the condition 37 00:02:18,820 --> 00:02:21,370 is less than or equal to ten is no longer true. 38 00:02:21,370 --> 00:02:23,080 In other words, when I equals eleven. 39 00:02:23,260 --> 00:02:25,870 So I should get when I run this go round bingo. 40 00:02:27,580 --> 00:02:34,900 I should get the numbers zero to 10 printed out one per line and I do I get the zero zero right up to 41 00:02:34,900 --> 00:02:35,200 ten. 42 00:02:35,650 --> 00:02:35,950 All right. 43 00:02:35,950 --> 00:02:37,390 So that's what a for loop is. 44 00:02:37,750 --> 00:02:39,220 And it's pretty simple. 45 00:02:39,220 --> 00:02:45,250 I can change this condition if I say if four is less than or equal to one and clear the screen here, 46 00:02:47,020 --> 00:02:51,640 I should only get zero and one and I get zero and one. 47 00:02:51,760 --> 00:02:55,240 So that's all the for loop is simplest thing in the world now. 48 00:02:55,240 --> 00:02:57,280 It's useful to be able to do this. 49 00:02:57,280 --> 00:03:03,010 There are many times when you want to run a particular operation, a certain number of iterations, 50 00:03:03,670 --> 00:03:05,740 but it's also useful to range over data. 51 00:03:06,100 --> 00:03:09,040 So let's create a slice. 52 00:03:09,040 --> 00:03:16,030 So I will say via let's just do the shorthand, I'll save my slice and I'll make a slice of strings 53 00:03:17,170 --> 00:03:20,980 is equal to a slice of string type string. 54 00:03:21,400 --> 00:03:31,070 And in parentheses I'll put dog, cat, horse, fish and banana just to be different, which are probably 55 00:03:31,070 --> 00:03:31,670 going to spell wrong. 56 00:03:31,670 --> 00:03:32,210 No, I got it right. 57 00:03:32,210 --> 00:03:32,620 There we go. 58 00:03:33,220 --> 00:03:36,610 Banana and I want to range over that slice. 59 00:03:36,620 --> 00:03:41,230 In other words, I want to start at the beginning of the slice and I want to print every entry in that 60 00:03:41,230 --> 00:03:42,700 slice to the terminal. 61 00:03:42,910 --> 00:03:50,080 Well, it's not that hard for and I'll put the I here to start with my index and then a value which 62 00:03:50,080 --> 00:03:54,640 I'll just call X is assigned range is a keyword. 63 00:03:55,120 --> 00:04:00,790 We're going to range over this data will range over my slice and then in parentheses we have to do something. 64 00:04:00,790 --> 00:04:05,320 Now, I've created two variables here because the range function actually returns. 65 00:04:05,830 --> 00:04:12,490 Both the current index where you are in the ranging through the data and the X stands for the current 66 00:04:12,490 --> 00:04:14,260 piece of data, what I'm currently looking at. 67 00:04:14,620 --> 00:04:18,810 So I actually don't want the index and I can get rid of that just by using the underscore instead. 68 00:04:18,820 --> 00:04:26,470 So all I have now is X and if I go log print line X there, there's my whole program, pretty straightforward. 69 00:04:26,770 --> 00:04:31,780 And what I'm doing is loading this slice of strings here. 70 00:04:31,780 --> 00:04:36,460 I'm ranging over it and every time I get a value I'm printing that value to the screen. 71 00:04:36,460 --> 00:04:41,080 So let's clear the screen and run this dog. 72 00:04:41,080 --> 00:04:42,860 Cat, horse, fish, banana. 73 00:04:42,940 --> 00:04:43,570 Perfect. 74 00:04:43,750 --> 00:04:50,980 All right, let's change my slice to my map and get rid of this and declare a map. 75 00:04:52,540 --> 00:04:59,590 My map is assigned the value of make a map string. 76 00:05:00,910 --> 00:05:07,840 Which I got a separate string of a map of strings, and I'm using a string to look up my values in the 77 00:05:07,840 --> 00:05:17,560 map and let's put some values in there, my map dog is equal to dog. 78 00:05:19,210 --> 00:05:24,100 Try that again, dog, and I'll duplicate that two more times. 79 00:05:24,940 --> 00:05:27,880 Fish and hat. 80 00:05:32,440 --> 00:05:33,430 I've created a map. 81 00:05:33,730 --> 00:05:36,160 It has three values dog, fish and hat. 82 00:05:36,520 --> 00:05:39,880 And I ranging through that map and I'm putting the information out. 83 00:05:39,880 --> 00:05:46,830 But this time let's put the index in there too, and we'll put I see what we get. 84 00:05:49,670 --> 00:05:50,510 Let me clear the street. 85 00:05:51,890 --> 00:05:58,050 Dog, dog, fish, fish, hot, hot was through the screen and do it again, hot dog, dog fish hates 86 00:05:58,060 --> 00:05:58,750 in a different odor. 87 00:05:58,750 --> 00:06:02,500 Remember I said maps are randomized, maps are randomized. 88 00:06:02,500 --> 00:06:07,480 You cannot depend upon a map being in the same order that the contents of a map will be in the same 89 00:06:07,480 --> 00:06:07,690 order. 90 00:06:07,690 --> 00:06:10,330 You enter the go compiler randomizer. 91 00:06:10,570 --> 00:06:14,020 I don't know why, but they must have some really good reason for doing it. 92 00:06:14,020 --> 00:06:14,650 So they do. 93 00:06:15,130 --> 00:06:18,670 So slices will remain whatever order they are at any given time. 94 00:06:18,670 --> 00:06:21,040 But maps are actually randomized. 95 00:06:21,310 --> 00:06:23,680 But I can range over both types. 96 00:06:23,950 --> 00:06:32,620 And again, if I created up here, if instead of this I had a user struct type user, which is a stretch 97 00:06:32,620 --> 00:06:42,580 to create my own data type and I put in first name string, last name string, and then I create instead 98 00:06:42,580 --> 00:06:53,710 of a map here of I mean this is slice my slice and create my slice as my slice of VA. 99 00:06:54,340 --> 00:06:58,450 My slice is a type user. 100 00:07:05,370 --> 00:07:07,350 I make a slice of users. 101 00:07:09,180 --> 00:07:11,170 OK, there we are. 102 00:07:11,220 --> 00:07:16,830 When I have a typo up here, what's my typo, first name, unresolved type, first name is of type string. 103 00:07:16,830 --> 00:07:17,640 I don't need Colon's. 104 00:07:17,640 --> 00:07:19,860 That's why I do that all the time. 105 00:07:20,280 --> 00:07:20,760 All right. 106 00:07:21,180 --> 00:07:25,880 So now I actually have a slice and it says here it's Skip because my slice is always nil. 107 00:07:25,890 --> 00:07:26,330 I know. 108 00:07:26,340 --> 00:07:27,420 Let's put some value in there. 109 00:07:27,810 --> 00:07:35,670 We'll put you one is of type user analysts put the values in there. 110 00:07:39,120 --> 00:07:45,300 First name Trevor, and I'll leave the second name empty for now, I just want to show you can range 111 00:07:45,300 --> 00:07:48,330 over this since the string, I got to put quotation marks around it. 112 00:07:48,360 --> 00:07:51,990 I think it's time for a coffee and then I'll create a user to. 113 00:07:56,270 --> 00:08:06,140 And we'll call this person Sam, and now open those to my slice, my slice equals prepend my slice, 114 00:08:06,170 --> 00:08:10,280 you one, and then I'll append you two to it as well. 115 00:08:11,330 --> 00:08:18,470 So now I have a slice of strings, a slice of users, which has a couple of values put in there. 116 00:08:18,470 --> 00:08:19,900 And now I should be able to range over this. 117 00:08:19,910 --> 00:08:25,010 So I've created a slice, my slice, which is a slice of type user users to find up here. 118 00:08:25,490 --> 00:08:29,350 I've created two users, only bothered populating the first field, but that's OK. 119 00:08:29,360 --> 00:08:31,030 You can put the second field in if you wish to. 120 00:08:31,490 --> 00:08:33,320 And now I can iterate through this. 121 00:08:33,470 --> 00:08:36,920 Now, if I leave it like this and run it, here's what I get. 122 00:08:38,600 --> 00:08:40,670 And it shows me what's in each of those. 123 00:08:40,670 --> 00:08:46,820 But if I actually refer to the fields that are in that struct first name and run it again, now, it 124 00:08:46,820 --> 00:08:50,900 will just print out the first name of each of those person for each of those people, plus the index, 125 00:08:50,930 --> 00:08:52,010 because I left that turned on. 126 00:08:53,020 --> 00:08:53,350 All right. 127 00:08:53,360 --> 00:08:54,770 That's how you range through data. 128 00:08:54,770 --> 00:09:01,970 You can use a for loop or you can use this this syntax here for index value is assigned range through 129 00:09:02,300 --> 00:09:03,920 whatever your structure happens to be. 130 00:09:04,640 --> 00:09:06,260 As long as your structure is changeable. 131 00:09:06,260 --> 00:09:09,080 Of course, you can't range through one variable of one type. 132 00:09:09,080 --> 00:09:13,490 So I can't range through a string because that's not a Wrangel data structure. 133 00:09:13,580 --> 00:09:18,060 But maps are, slices are and others are, as we'll see as time goes on. 134 00:09:18,440 --> 00:09:18,800 All right. 135 00:09:18,920 --> 00:09:21,920 That's it for ranging through data and looping through data.