1 00:00:01,380 --> 00:00:05,270 Everybody Mark Price you're at slopes dot com. 2 00:00:05,300 --> 00:00:10,790 Today we are going to build nothing at all. 3 00:00:10,890 --> 00:00:13,410 We're in a code in the playground though. 4 00:00:15,580 --> 00:00:18,560 And we got excited like we're going to build our first iOS app. 5 00:00:18,560 --> 00:00:20,990 I'm sorry I tricked you. 6 00:00:21,200 --> 00:00:23,990 I mean open a new playground here. 7 00:00:24,440 --> 00:00:25,920 Move it on over to the screen. 8 00:00:26,030 --> 00:00:26,750 OK playground. 9 00:00:26,750 --> 00:00:29,270 We're going to call this one. 10 00:00:29,560 --> 00:00:31,370 Re me. 11 00:00:31,400 --> 00:00:32,310 OK. 12 00:00:32,620 --> 00:00:32,870 OK. 13 00:00:32,870 --> 00:00:34,990 We're going to talk about race today. 14 00:00:35,250 --> 00:00:42,140 An NRA is incredibly important data structure and foundational data structure that you need to learn. 15 00:00:42,290 --> 00:00:47,790 So we're going to call this raise save it right there. 16 00:00:47,800 --> 00:00:52,640 So let's talk about why we need to raise. 17 00:00:52,840 --> 00:01:03,150 So let's say that we have an app and it manages our employees and our employees all of us our let's 18 00:01:03,150 --> 00:01:10,310 say it's a salary manager so let's we've got our employee one salary. 19 00:01:10,370 --> 00:01:11,130 OK. 20 00:01:11,570 --> 00:01:17,750 And let's say equals forty five thousand dollars a year. 21 00:01:18,060 --> 00:01:28,510 You know our employee two salary equals fifty four dollars. 22 00:01:30,800 --> 00:01:46,920 All right our employee three salary equals $100000 a year for loyalty or salary equals $20000. 23 00:01:47,050 --> 00:01:47,980 This dude's an intern. 24 00:01:47,980 --> 00:01:49,180 He ain't getting paid nothing. 25 00:01:49,180 --> 00:01:49,720 All right. 26 00:01:49,960 --> 00:01:52,410 So we up for employees here. 27 00:01:52,450 --> 00:01:52,770 OK. 28 00:01:52,780 --> 00:01:53,970 So cool. 29 00:01:53,980 --> 00:01:58,510 You know we've got a list of data here but what if I need to work with things or what if I need to fire 30 00:01:58,510 --> 00:01:59,240 somebody. 31 00:01:59,450 --> 00:02:00,660 OK how do I get rid of this. 32 00:02:00,670 --> 00:02:02,270 Well this isn't really helpful is it. 33 00:02:02,270 --> 00:02:09,010 These are just four variables we had are right a lot of code over and over and over again and we have 34 00:02:09,010 --> 00:02:09,800 four employees here. 35 00:02:09,820 --> 00:02:14,990 Maybe it makes sense to structure this in a slightly better way and we can do that. 36 00:02:15,070 --> 00:02:18,320 We can do something we can create something called an array. 37 00:02:18,810 --> 00:02:23,620 And so to declare a you can of course use a constant or very long. 38 00:02:23,710 --> 00:02:25,510 In our case we use a variable. 39 00:02:25,570 --> 00:02:26,930 So we can change it around. 40 00:02:26,990 --> 00:02:30,330 We do just call employees or employee salaries. 41 00:02:30,340 --> 00:02:32,080 All we care about is the salaries right now. 42 00:02:32,080 --> 00:02:46,730 So what we can do is say 45000 Oh comma four thousand one hundred one hundred thousand over 20. 43 00:02:46,940 --> 00:02:47,490 Oh. 44 00:02:47,860 --> 00:02:48,830 Oh OK. 45 00:02:48,880 --> 00:02:55,680 So what we just done here is we've created an array of type and that has four elements in it. 46 00:02:55,690 --> 00:02:57,380 Those are all proper terms. 47 00:02:57,550 --> 00:03:00,440 An array has X amount of elements in it. 48 00:03:00,820 --> 00:03:01,230 OK. 49 00:03:01,240 --> 00:03:02,900 And again this is an array of type. 50 00:03:02,930 --> 00:03:04,340 And so you create one. 51 00:03:04,660 --> 00:03:10,900 You can create an array initialized with data right from the get go by putting the left square bracket 52 00:03:10,960 --> 00:03:16,270 and the right square bracket or brace the left brace and the right brace OK. 53 00:03:16,690 --> 00:03:19,020 And for for terms. 54 00:03:19,080 --> 00:03:21,670 Those are braces and these are brackets. 55 00:03:21,670 --> 00:03:26,350 Technically people do say them interchangeably and sometimes I make mistakes but just know these are 56 00:03:26,350 --> 00:03:29,460 brackets and these are braces now OK. 57 00:03:29,460 --> 00:03:32,720 And then you separate the values in the array with a comma. 58 00:03:32,740 --> 00:03:37,450 What was the what would happen if I tried putting a string in one of these elements here. 59 00:03:43,560 --> 00:03:46,090 Interesting is yelling at me. 60 00:03:46,170 --> 00:03:47,930 No it's not OK. 61 00:03:48,300 --> 00:03:56,620 But what if I said this array has to be of type int. 62 00:03:56,640 --> 00:03:57,830 Now it's yelling at me. 63 00:03:58,020 --> 00:04:01,440 Oh interesting it can't be used with an array literal. 64 00:04:01,440 --> 00:04:06,870 So when I did this it worked when I put it in front of it it did not. 65 00:04:06,870 --> 00:04:10,080 That's because you can store various types in an array. 66 00:04:10,360 --> 00:04:16,080 But if you want to explicitly declare a type of an array it must all have the exact same type and are 67 00:04:16,140 --> 00:04:20,060 in our case we want it to be we want it to be integers. 68 00:04:20,220 --> 00:04:20,970 OK. 69 00:04:21,570 --> 00:04:25,630 Eric Sujan these are integers these are doubles because of the point zero at the end. 70 00:04:25,780 --> 00:04:27,000 OK. 71 00:04:27,750 --> 00:04:28,860 So pretty cool right. 72 00:04:28,890 --> 00:04:32,310 So that's how we create an array and we can do different things with an array. 73 00:04:32,310 --> 00:04:36,090 Let's say we want to add a new employee or rather than creating a whole new variable and play five you 74 00:04:36,090 --> 00:04:38,790 know we could just go do something like this. 75 00:04:38,790 --> 00:04:45,610 Employee employee salaries there is not a pen. 76 00:04:45,630 --> 00:04:51,960 Let's add a new employee salary and let's make this one thirty nine thousand nine thousand dollars and 77 00:04:51,960 --> 00:04:53,470 34 cents a year. 78 00:04:53,970 --> 00:05:00,360 So what we've just done is we've added a fifth element to the array which I think is pretty cool. 79 00:05:00,360 --> 00:05:07,830 So at this point we can actually print some things or we can print the count so employee salaries don't 80 00:05:07,830 --> 00:05:13,070 count at this point in time is for. 81 00:05:13,070 --> 00:05:17,100 And by the way if you see this end here it means new line it's creating a new line for us so the next 82 00:05:17,100 --> 00:05:20,110 thing prints on the next line that's why it's there you don't need to worry about it. 83 00:05:20,330 --> 00:05:21,280 OK. 84 00:05:21,870 --> 00:05:26,260 And then last print after you've added employee salaries don't count. 85 00:05:26,720 --> 00:05:27,750 OK. 86 00:05:28,330 --> 00:05:32,370 It now has five. 87 00:05:32,380 --> 00:05:33,260 There we go. 88 00:05:33,310 --> 00:05:34,520 So it now is five. 89 00:05:34,630 --> 00:05:35,610 OK. 90 00:05:35,620 --> 00:05:41,590 And the doc count is a property it's a variable but it's called a property of the end of an array and 91 00:05:41,590 --> 00:05:46,750 it will tell you how many elements are in the array and this dot is actually calling a function as you 92 00:05:46,750 --> 00:05:49,640 can see with the left parentheses and the right parentheses. 93 00:05:50,170 --> 00:05:52,250 And you can append an element into that array. 94 00:05:52,270 --> 00:05:59,930 Now if this array is a double k am I able. 95 00:06:00,480 --> 00:06:02,680 Oh didn't like that very much did it. 96 00:06:02,970 --> 00:06:04,130 Why is it yelling at me. 97 00:06:04,390 --> 00:06:05,920 Oh my bad. 98 00:06:07,280 --> 00:06:07,910 Area. 99 00:06:08,150 --> 00:06:11,910 So the type is double when it when it's a type of double or array. 100 00:06:11,960 --> 00:06:14,710 You put the braces around it. 101 00:06:14,750 --> 00:06:15,320 OK. 102 00:06:15,560 --> 00:06:23,390 So here if I wanted to append a string like so you shouldn't let me in because it's expecting a double. 103 00:06:23,570 --> 00:06:25,400 All right. 104 00:06:25,400 --> 00:06:29,060 So now what we've done is we've given an explicit type. 105 00:06:29,060 --> 00:06:30,950 This is an array. 106 00:06:31,020 --> 00:06:34,600 See the braces of type double and boom. 107 00:06:34,670 --> 00:06:36,090 There you have it right there. 108 00:06:36,090 --> 00:06:37,550 That's pretty cool. 109 00:06:37,580 --> 00:06:39,050 You can also do different things as well. 110 00:06:39,110 --> 00:06:42,420 Let's see if we can specify it like this. 111 00:06:46,580 --> 00:06:51,620 Interesting it's letting us define it a different way and this is the exact same things we did before. 112 00:06:51,620 --> 00:06:51,960 OK. 113 00:06:51,980 --> 00:06:57,480 So just using different syntax array of type double the more common way is this. 114 00:06:58,160 --> 00:06:59,180 OK. 115 00:06:59,870 --> 00:07:00,890 And then we've appended it. 116 00:07:00,920 --> 00:07:06,030 What if I want to remove an element let's say we just fired employee number two. 117 00:07:06,080 --> 00:07:08,930 So this one right here how do we get rid of this employee. 118 00:07:08,930 --> 00:07:15,590 Well we can to say employee salaries dot remove X and it wants to index. 119 00:07:15,620 --> 00:07:21,980 And we're going to say 1 you're like wait a minute we're not getting rid of the first employee We're 120 00:07:21,980 --> 00:07:23,480 going to get rid of the second employee. 121 00:07:23,480 --> 00:07:24,480 What's going on. 122 00:07:24,830 --> 00:07:26,940 Well here's a secret. 123 00:07:27,220 --> 00:07:29,360 I mean to tell you and it's not a secret at all. 124 00:07:29,570 --> 00:07:32,680 So it's not a secret and you need to know this because it is so important. 125 00:07:32,690 --> 00:07:34,210 Arrays start at zero. 126 00:07:34,250 --> 00:07:40,220 Every array in pretty much every programming language always starts at zero so the zero index is number 127 00:07:40,220 --> 00:07:40,520 one. 128 00:07:40,520 --> 00:07:45,150 So this is 0 1 2 and 3. 129 00:07:45,440 --> 00:07:45,780 OK. 130 00:07:45,800 --> 00:07:51,230 Very important so to get rid of Employee 2 we say 1 and this may be confusing at first but always if 131 00:07:51,230 --> 00:07:55,700 you get confused or is this basically if you want to start at once started one but then remember you 132 00:07:55,700 --> 00:07:57,570 need a minus one because it starts at zero. 133 00:07:57,740 --> 00:07:59,700 OK so we removed unemploy. 134 00:08:00,170 --> 00:08:07,220 So now I say I print the employee salaries don't count. 135 00:08:07,400 --> 00:08:09,260 It should now be back for. 136 00:08:09,440 --> 00:08:10,850 So it's gone. 137 00:08:11,360 --> 00:08:13,670 So you can add things to an array. 138 00:08:13,670 --> 00:08:18,710 You can remove things one way an array should be used whenever you need a collection of something to 139 00:08:18,710 --> 00:08:19,370 be together. 140 00:08:19,380 --> 00:08:22,760 That's a it's a collection that's what it is a collection of things. 141 00:08:22,760 --> 00:08:23,310 OK. 142 00:08:23,570 --> 00:08:32,660 You know so similarly you know if I was a teacher in a classroom which I am oh you might have a list 143 00:08:32,690 --> 00:08:34,080 or an array of students right. 144 00:08:34,090 --> 00:08:35,580 So students. 145 00:08:35,600 --> 00:08:36,160 OK. 146 00:08:36,440 --> 00:08:41,700 And we're going to do this time as we're going to just create an empty array. 147 00:08:41,720 --> 00:08:46,460 So what you do is you put the square braces or just the braces with the type in it and then you put 148 00:08:46,460 --> 00:08:48,650 the parentheses at the end. 149 00:08:48,680 --> 00:08:49,860 Remember this is an equal sign. 150 00:08:49,880 --> 00:08:53,740 What this is doing is it's creating an empty array of type string. 151 00:08:53,750 --> 00:08:59,850 So if I print the count print students dot count it should be zero. 152 00:09:00,190 --> 00:09:04,470 OK this is really important that you initialize an array. 153 00:09:04,520 --> 00:09:11,850 So if I say if I was to do this for students students list to get and I just said it's an array of type 154 00:09:12,200 --> 00:09:13,420 string like that. 155 00:09:13,700 --> 00:09:22,620 And then if I tried to do something like this student list to dot a pen and we say John Adams. 156 00:09:22,830 --> 00:09:24,880 See what happens. 157 00:09:25,070 --> 00:09:25,930 We have a crash. 158 00:09:25,930 --> 00:09:30,240 This will crash or at variable student lists to pass by reference before being initialized. 159 00:09:30,410 --> 00:09:32,270 What that means is you have not initialized it. 160 00:09:32,270 --> 00:09:36,100 This has just been declared and not initialized. 161 00:09:36,110 --> 00:09:37,480 This one is initialized. 162 00:09:37,520 --> 00:09:41,900 This one is not OK as you can see by the parentheses here and this would actually crash application 163 00:09:41,900 --> 00:09:45,920 C always must initialize an array before you can actually use it. 164 00:09:45,920 --> 00:09:48,410 And the same goes for variables any type of variable. 165 00:09:48,530 --> 00:09:49,070 OK. 166 00:09:49,220 --> 00:09:51,360 So this is no bueno. 167 00:09:51,980 --> 00:09:57,850 OK so we've we've now crashed our program was going to crash. 168 00:09:58,160 --> 00:09:59,320 I think it crashed for different reasons. 169 00:09:59,330 --> 00:10:03,560 But so now we can add student straight students that are penned. 170 00:10:03,860 --> 00:10:10,070 You know they say John students got a pen. 171 00:10:11,230 --> 00:10:17,770 Students pen say students type pen 172 00:10:20,430 --> 00:10:32,630 jingle students and crash I was great. 173 00:10:32,730 --> 00:10:33,470 All right. 174 00:10:33,960 --> 00:10:41,400 Students panned either. 175 00:10:41,520 --> 00:10:43,260 Now this may seem like what are you doing. 176 00:10:43,260 --> 00:10:43,940 A lot of stuff here. 177 00:10:43,950 --> 00:10:48,900 But mom this actually saves us a lot of code in the end by using arrays versus creating a bunch of different 178 00:10:48,900 --> 00:10:50,630 variables. 179 00:10:50,850 --> 00:10:51,210 So anyway 180 00:10:54,150 --> 00:10:59,150 we got I just wanted to show you this cool little pyramid here of what happens when you add things so 181 00:10:59,150 --> 00:11:02,900 we add one element two elements three elements four elements 5 and 6. 182 00:11:02,900 --> 00:11:08,480 Ok Allison we want to get rid of Jose because he's clearly not part of this song. 183 00:11:08,780 --> 00:11:09,720 I mean the student. 184 00:11:09,770 --> 00:11:17,520 So we can just say what does he talking about song remember from from grade school. 185 00:11:17,650 --> 00:11:18,390 Jake. 186 00:11:18,530 --> 00:11:21,020 Jingle Hummer's. 187 00:11:21,770 --> 00:11:25,990 Well you're like you guys are like stupid American. 188 00:11:26,180 --> 00:11:26,930 They don't teach that. 189 00:11:26,930 --> 00:11:27,790 Where you're from I get it. 190 00:11:27,830 --> 00:11:29,020 I get it. 191 00:11:29,120 --> 00:11:31,830 What we want to remove Jose because he doesn't belong in the song. 192 00:11:31,850 --> 00:11:33,730 So which index should we get rid of. 193 00:11:33,740 --> 00:11:38,420 Tell me one two three four five or six. 194 00:11:38,420 --> 00:11:39,500 You said two that's right. 195 00:11:39,560 --> 00:11:42,820 Because 2 0 1 2. 196 00:11:42,860 --> 00:11:44,830 So Jose is no longer in our song. 197 00:11:44,930 --> 00:11:48,740 And now if I print the array and say to students 198 00:11:52,490 --> 00:11:53,460 John. 199 00:11:53,560 --> 00:11:55,450 Jean Hammersmith. 200 00:11:55,900 --> 00:12:00,970 OK so lots of fun things you can do with an array and if you want to see all the things that are available 201 00:12:00,970 --> 00:12:07,420 for you when it does command click append here and is going to take us to the documentation and you 202 00:12:07,420 --> 00:12:09,920 can do different things different type of append functions. 203 00:12:10,000 --> 00:12:17,620 Remove the last element insert a new element add an index remove an element add index remove all k a 204 00:12:17,620 --> 00:12:22,120 whole bunch of things you can do with arrays and we've just barely scratched the surface and arrays 205 00:12:22,120 --> 00:12:26,120 are also commonly used hand-in-hand with loops which we haven't talked about yet. 206 00:12:26,130 --> 00:12:27,700 But you'll see that you'll see that to come. 207 00:12:27,700 --> 00:12:31,210 So it's a collection of data allows you to work with different things. 208 00:12:31,210 --> 00:12:36,940 So I think pleura when you think of an array so you know lots of students make an array a list of teachers 209 00:12:36,940 --> 00:12:39,620 make an array a list of anything make an array. 210 00:12:39,940 --> 00:12:46,500 And now you're starting to think of better ways to organize your code rather than doing stuff like this. 211 00:12:46,650 --> 00:12:47,090 OK. 212 00:12:47,200 --> 00:12:50,970 Start using arrays this collection types and that's it. 213 00:12:50,980 --> 00:12:55,990 There's so much more to go into arrays but this is the basic foundational building blocks that I'm hoping 214 00:12:55,980 --> 00:12:56,300 for. 215 00:12:56,300 --> 00:12:57,290 Mark right. 216 00:12:57,370 --> 00:12:59,620 Slopes dot com. 217 00:12:59,740 --> 00:13:01,960 Stay tuned for our exciting next episode.