1 00:00:08,070 --> 00:00:09,120 Hey buddy what's going on. 2 00:00:09,120 --> 00:00:14,730 This is Caleb with Debb slopes dot com and in this video we're going to talk about optionals and optionals 3 00:00:14,730 --> 00:00:17,850 are an amazing part of the swift programming language. 4 00:00:18,030 --> 00:00:22,610 And I want you to think about an optional sort of like a rapper or like a box. 5 00:00:22,710 --> 00:00:23,210 OK. 6 00:00:23,370 --> 00:00:27,030 Now it can hold something right like a box can have something inside of it. 7 00:00:27,030 --> 00:00:32,880 A wrapper can have some type of maybe food or even like a drink if you think of like a drink container 8 00:00:33,900 --> 00:00:36,770 it can hold something or it can be empty. 9 00:00:36,810 --> 00:00:37,090 OK. 10 00:00:37,110 --> 00:00:42,420 That's like that's what an optional is sort of like it can have a value or it cannot have a value. 11 00:00:42,420 --> 00:00:46,020 Now imagine you got a package delivered from Amazon. 12 00:00:46,020 --> 00:00:52,260 When you pick it up off your front porch there can be something inside but it's possible that at the 13 00:00:52,260 --> 00:00:58,320 fulfillment center there was a mishap and maybe your box is empty which of course that would be really 14 00:00:58,320 --> 00:01:02,070 disappointing and kind of a lame thing but that is possible. 15 00:01:02,070 --> 00:01:08,970 The idea behind optionals is that we can safely use the box without having to worry what's inside. 16 00:01:09,190 --> 00:01:09,870 OK. 17 00:01:10,110 --> 00:01:17,270 That is the cool thing about optionals So let's go ahead let's pull open a brand new X code playground. 18 00:01:17,430 --> 00:01:23,640 So open up X code and in this little welcome to X code menu click get started with a playground and 19 00:01:23,670 --> 00:01:25,970 we're going to do a blank playground. 20 00:01:26,190 --> 00:01:31,480 And I'm going to call this shoes optional. 21 00:01:31,630 --> 00:01:36,310 Just you know instead of clothing optional just say shoes optional little more appropriate anyway. 22 00:01:36,840 --> 00:01:39,580 Create it and let's pull it open. 23 00:01:39,630 --> 00:01:40,860 Full size. 24 00:01:40,860 --> 00:01:41,630 There we go. 25 00:01:41,670 --> 00:01:47,190 By the way if you're wondering how I'm doing that I can make it take up the left side of the screen 26 00:01:47,220 --> 00:01:48,660 the right side of the screen. 27 00:01:48,840 --> 00:01:49,720 Anything like that. 28 00:01:49,720 --> 00:01:50,280 Pretty neat. 29 00:01:50,310 --> 00:01:53,610 It's a little app called shoot. 30 00:01:53,610 --> 00:01:55,680 What is it called a magnet. 31 00:01:55,680 --> 00:01:56,200 Right. 32 00:01:56,250 --> 00:01:56,870 It's called Magnet. 33 00:01:56,870 --> 00:01:58,440 There's another one called flexi glass. 34 00:01:58,440 --> 00:02:01,040 I just happened to like magnet a little bit better. 35 00:02:01,080 --> 00:02:02,400 Anyway let's get started. 36 00:02:02,400 --> 00:02:08,280 So I'm going to go ahead and get rid of that variable there and I'm going to get rid of that little 37 00:02:08,280 --> 00:02:10,480 commented line there. 38 00:02:10,620 --> 00:02:15,890 And I want to show you how optionals can work and I'm going to use some images to represent them. 39 00:02:16,020 --> 00:02:20,700 So I'm going to create an optional image and I'm going to create a non-optional image so I'm going to 40 00:02:20,700 --> 00:02:23,320 show you how you declare a variable as optional. 41 00:02:23,610 --> 00:02:32,430 So go ahead and type let optional image and we're going to make it of Type II image but I'm going to 42 00:02:32,430 --> 00:02:37,890 declare it as optional by putting a question mark at the end of the type declaration. 43 00:02:37,890 --> 00:02:41,190 Now of course as it currently exists it is optional. 44 00:02:41,340 --> 00:02:42,900 It can have a value. 45 00:02:42,930 --> 00:02:50,210 It can not have a value meaning it's able to be nil or it's able to be or to have a value. 46 00:02:50,400 --> 00:02:55,950 And I'm going to go ahead and give it a value just for the explanation purposes of this. 47 00:02:56,070 --> 00:03:02,040 And so I'm going to insert an image literal from the editor menu and I'm going to drop in that image 48 00:03:02,040 --> 00:03:02,790 right there. 49 00:03:03,030 --> 00:03:03,900 OK. 50 00:03:03,900 --> 00:03:07,000 Now I'm going to add a viewer so we can see the image. 51 00:03:07,010 --> 00:03:08,080 All righty. 52 00:03:08,140 --> 00:03:09,390 And that's great. 53 00:03:09,390 --> 00:03:10,470 So there it is. 54 00:03:10,470 --> 00:03:16,290 This is an image representation of what an optional is like it's a box but it can be empty meaning it 55 00:03:16,290 --> 00:03:18,150 can have a nil value. 56 00:03:18,150 --> 00:03:25,240 Now let's go ahead and create let non optional image and we're going to make that of type I image. 57 00:03:25,480 --> 00:03:25,760 OK. 58 00:03:25,770 --> 00:03:29,490 And we're not going to put a question mark meaning it has a literal value. 59 00:03:29,490 --> 00:03:35,140 We're going to go ahead and insert an image literal and I'm going to use this image to represent that. 60 00:03:35,160 --> 00:03:38,070 And when I pull open this viewer you can see what I mean. 61 00:03:38,190 --> 00:03:40,480 This non-optional image. 62 00:03:40,650 --> 00:03:45,210 Well it's an image but it represents an optional with a value of five. 63 00:03:45,210 --> 00:03:49,690 So this optional can have a value of 5 or it can have a value of nil. 64 00:03:49,830 --> 00:03:51,510 OK that's pretty cool. 65 00:03:51,510 --> 00:03:56,280 Now I'm going to show you ways that you can actually use optionals and then some things we need to be 66 00:03:56,280 --> 00:04:01,530 careful about as well as at the end I'm going to show you kind of a real life example of using optionals. 67 00:04:01,650 --> 00:04:05,750 So we're going to go ahead and talk about forced unwrapping. 68 00:04:05,820 --> 00:04:08,020 So go ahead and type a variable here. 69 00:04:08,040 --> 00:04:11,480 Var optional number. 70 00:04:12,480 --> 00:04:14,690 And we're going to make it of type int. 71 00:04:14,730 --> 00:04:16,620 Although we're going to make it optional. 72 00:04:16,830 --> 00:04:22,000 OK so this could be for something maybe that we don't know if it's going to have a value or not. 73 00:04:22,380 --> 00:04:25,830 Although I'm going to set it to have a value of 5. 74 00:04:26,280 --> 00:04:31,870 So it's optional but it has a value of 5 and I'll show you how this works in just a moment. 75 00:04:32,040 --> 00:04:38,820 Next we're going to go ahead and just create another variable of type and and make it equal to 5 as 76 00:04:38,850 --> 00:04:39,270 well. 77 00:04:39,270 --> 00:04:42,160 Now you'll notice the second one is not optional. 78 00:04:42,210 --> 00:04:53,180 So what I can do here is I can say if optional number is not equal to nil OK meaning if it is not nil. 79 00:04:53,370 --> 00:05:01,350 We're going to print and we're going to put something in the print statement that says optional number 80 00:05:02,520 --> 00:05:11,510 has a value of and we'll use string interpolation here to pull out the value of optional number and 81 00:05:11,510 --> 00:05:17,900 we will go like that and pass it the value for optional number because we have given it a value right. 82 00:05:18,200 --> 00:05:22,670 We say optional number has a value of optional number. 83 00:05:22,670 --> 00:05:28,020 Now you'll notice when it prints out it says optional number has a value of optional 5. 84 00:05:28,250 --> 00:05:31,260 Now you're wondering well why is that. 85 00:05:31,280 --> 00:05:34,900 This is a way that swift keeps us safe when we're programming. 86 00:05:35,030 --> 00:05:40,820 Since it is optional it's passing in the value for 5 but it's keeping track that it's an optional value 87 00:05:40,820 --> 00:05:42,500 and that it could be nil. 88 00:05:42,500 --> 00:05:50,190 Now watch what happens if I change it to nil meaning I give it a nil value a value of nothing. 89 00:05:50,210 --> 00:05:55,230 You'll notice nothing happens because we're checking to see if optional number is nil. 90 00:05:55,280 --> 00:05:57,530 So let's turn it back to 5. 91 00:05:57,620 --> 00:06:00,740 But I said we're talking about force unwrapping. 92 00:06:01,010 --> 00:06:05,310 Now this optional number variable has an optional value of 5. 93 00:06:05,330 --> 00:06:11,780 But in order to actually access the real value we need to use an exclamation mark to force unwrap it. 94 00:06:11,900 --> 00:06:14,840 It's like we're opening the box and taking the value 5 out. 95 00:06:14,830 --> 00:06:17,190 We're actually getting it from the box. 96 00:06:17,270 --> 00:06:18,800 So that's Force unwrapping. 97 00:06:18,800 --> 00:06:22,580 But watch what happens if I change this. 98 00:06:22,610 --> 00:06:26,430 Let's just say I take away this conditional check. 99 00:06:26,460 --> 00:06:29,490 This is to show you the danger of using an optional. 100 00:06:29,570 --> 00:06:38,370 Watch what happens if I change it to nil fatal error unexpectedly found nil while unwrapping an optional 101 00:06:38,370 --> 00:06:39,300 value. 102 00:06:39,720 --> 00:06:40,560 That's a problem. 103 00:06:40,560 --> 00:06:44,260 So this is where we need to be careful with force on wrapping. 104 00:06:44,460 --> 00:06:50,950 You need to basically set up conditional code to check to make sure that it's not nil and you might 105 00:06:50,950 --> 00:06:53,340 be wondering well why would I ever have an optional value. 106 00:06:53,340 --> 00:06:57,360 Think about if you're pulling data from a server and you're not sure that a certain value will come 107 00:06:57,360 --> 00:06:59,650 back of a certain type every single time. 108 00:06:59,670 --> 00:07:06,510 It would be better to set it as nil or sorry I said as an optional in case the value returns nil so 109 00:07:06,630 --> 00:07:08,980 if that were to happen you could say if it's not nil. 110 00:07:09,000 --> 00:07:10,920 Do something else. 111 00:07:11,190 --> 00:07:15,430 And then here you could basically set it up so that it would handle any errors. 112 00:07:15,480 --> 00:07:18,720 Ok that is just one way you could use optionals. 113 00:07:18,740 --> 00:07:20,420 It gives us the option right. 114 00:07:20,430 --> 00:07:21,680 That's the optional thing. 115 00:07:21,810 --> 00:07:27,230 It gives us the option of basically using a value or a non-value. 116 00:07:27,270 --> 00:07:27,960 So here we go. 117 00:07:27,960 --> 00:07:28,980 Let's go ahead and move on. 118 00:07:28,980 --> 00:07:30,120 That's for Sun wrapping. 119 00:07:30,120 --> 00:07:37,160 That's how you take an optional value and you force unwrap it into something that is an actual value. 120 00:07:37,170 --> 00:07:38,010 Pretty cool. 121 00:07:38,190 --> 00:07:41,680 Now I'm going to go ahead and just close these viewers here they're giving us some trouble. 122 00:07:42,210 --> 00:07:43,720 And let's move on. 123 00:07:43,920 --> 00:07:49,140 So next up we're going to go ahead and check out something called optional binding. 124 00:07:49,310 --> 00:07:49,960 OK. 125 00:07:50,130 --> 00:07:54,660 Now what we're going to do with optional binding is we're going to basically take an optional value 126 00:07:54,870 --> 00:07:58,110 and we're going to bind it to a non optional constant. 127 00:07:58,110 --> 00:08:04,890 But the cool thing is that we will use an IF statement to handle what happens if the optional number 128 00:08:04,890 --> 00:08:05,790 comes in as nil. 129 00:08:05,790 --> 00:08:06,860 So check it out. 130 00:08:06,990 --> 00:08:12,740 If we go ahead and type if left and then we can say constant number. 131 00:08:12,910 --> 00:08:16,320 OK so we just created a constant called constant number. 132 00:08:16,440 --> 00:08:20,300 We're going to set it to be equal to optional number. 133 00:08:20,310 --> 00:08:25,630 All right so now we have a constant that has a definite value of optional number. 134 00:08:25,920 --> 00:08:29,800 But what happens if constant number is not. 135 00:08:30,090 --> 00:08:34,710 What if we can't set the value of constant number what if optional number is actually nil that would 136 00:08:34,710 --> 00:08:35,670 cause a problem. 137 00:08:35,850 --> 00:08:41,620 So what we're going to do is we're going to print let's print out what we see here. 138 00:08:41,760 --> 00:08:46,790 Constant number has a value of. 139 00:08:46,880 --> 00:08:49,650 And we'll print out constant number. 140 00:08:50,070 --> 00:08:50,690 OK. 141 00:08:51,030 --> 00:08:56,850 Now when this runs you'll see that it actually does print k. 142 00:08:57,120 --> 00:09:04,130 We are creating a constant called constant number and when it runs lets run it and you'll see it'll 143 00:09:04,140 --> 00:09:08,490 print out constant number has a value of constant number but it's not doing anything. 144 00:09:08,700 --> 00:09:11,000 That's because our value is nil. 145 00:09:11,010 --> 00:09:15,900 And that's where our else block comes in when we're doing optional binding we're basically binding an 146 00:09:15,900 --> 00:09:17,660 optional value to a constant. 147 00:09:17,790 --> 00:09:22,170 But we're using an if else so that we can handle both cases value or no value. 148 00:09:22,170 --> 00:09:27,580 So if we can create the constant and set it to be optional number it'll print that out. 149 00:09:27,600 --> 00:09:32,560 Otherwise we will print what is it. 150 00:09:32,700 --> 00:09:38,670 Let's see optional number is nil because that's what it means it must be nil if that's if that's what 151 00:09:38,670 --> 00:09:41,840 is happening and as you can see optional number is nil. 152 00:09:41,940 --> 00:09:45,460 And so that is where we could handle errors just like I said above. 153 00:09:45,510 --> 00:09:52,240 But the cool thing is that we can use constant number as a way of creating a non optional value. 154 00:09:52,250 --> 00:09:54,540 You notice how we don't have to force on wrap this. 155 00:09:54,540 --> 00:10:00,840 Watch what happens when I set it to be a value of five optional number and Konst that number has a value 156 00:10:00,840 --> 00:10:06,780 of five that basically allows us to create a non-optional constant from an optional. 157 00:10:06,780 --> 00:10:07,710 Pretty cool. 158 00:10:08,010 --> 00:10:13,650 So that is optional binding you know what let me go ahead and put some notes here so we don't forget 159 00:10:13,740 --> 00:10:20,140 this was force unwrapping force unwrapping. 160 00:10:20,160 --> 00:10:21,710 Whoops. 161 00:10:22,260 --> 00:10:23,330 Anyway moving on. 162 00:10:23,430 --> 00:10:25,860 So let's go ahead and I want to show you another example. 163 00:10:25,860 --> 00:10:31,920 I'm going to create a function here called in printer and it's basically just going to print out an 164 00:10:31,920 --> 00:10:33,210 integer value. 165 00:10:33,210 --> 00:10:37,890 Now I can also use optional binding within the guard let check it out. 166 00:10:38,130 --> 00:10:42,130 Guard let constant number just like above. 167 00:10:42,420 --> 00:10:45,880 And we're going to set it to be equal to optional number. 168 00:10:46,260 --> 00:10:48,930 If we can't do that right. 169 00:10:48,930 --> 00:10:50,140 Meaning if it's nil. 170 00:10:50,160 --> 00:10:53,650 We're just going to go ahead and say return just like that. 171 00:10:53,670 --> 00:11:02,310 Now assuming that we do get a value we're going to go ahead and print constant number has a value value 172 00:11:02,430 --> 00:11:02,970 of 173 00:11:06,070 --> 00:11:10,360 what is it optional number constant number we'll just say constant number because it'll be the same 174 00:11:10,360 --> 00:11:11,700 as optional number. 175 00:11:11,710 --> 00:11:12,250 Cool cool. 176 00:11:12,250 --> 00:11:17,270 So we've used the guard let to say if optional number has a value. 177 00:11:17,290 --> 00:11:21,350 Set it to be equal to or set constant number to be equal to optional number. 178 00:11:21,460 --> 00:11:23,580 Otherwise return and get out of the function. 179 00:11:23,620 --> 00:11:27,780 So let's go ahead and let's call it printer wups. 180 00:11:27,800 --> 00:11:28,450 There we go. 181 00:11:28,550 --> 00:11:32,150 And when it runs you'll see that it prints it out right there a third time. 182 00:11:32,150 --> 00:11:37,270 But watch what happens if I set optional number to be equal to nil or have no value. 183 00:11:37,430 --> 00:11:38,480 It doesn't print. 184 00:11:38,570 --> 00:11:45,350 The only one that prints is our first one where we forced unwrap the value or sorry where it where we 185 00:11:45,650 --> 00:11:46,480 tried to bind it. 186 00:11:46,490 --> 00:11:50,210 But if we couldn't bind it then we would print out optional numbers nil. 187 00:11:50,270 --> 00:11:53,850 So change it back to have a value of five and we're going to move on now. 188 00:11:54,080 --> 00:12:02,190 We're going to talk about what are called implicitly implicitly unwrapped optionals. 189 00:12:02,190 --> 00:12:02,800 OK. 190 00:12:03,080 --> 00:12:08,950 So implicitly unwrapped optional is basically where we are going to force unwrap a value from the very 191 00:12:08,950 --> 00:12:09,690 beginning. 192 00:12:09,760 --> 00:12:14,940 So to do that we can just say I'm going to assume that a value is coming in as maybe 5. 193 00:12:14,950 --> 00:12:24,040 So let assumed value of type int equals 5 but if we're going to make this implicitly unwrapped we're 194 00:12:24,040 --> 00:12:26,130 going to go ahead and put an exclamation mark. 195 00:12:26,140 --> 00:12:28,950 That means we are force on wrapping that value. 196 00:12:28,960 --> 00:12:40,400 So what we're going to do next is we can just say let implicit value of type int equals assumed value. 197 00:12:40,780 --> 00:12:41,740 Okay. 198 00:12:41,980 --> 00:12:47,260 So we are able to create a value can see over here that it does create a value of 5 but watch what happens 199 00:12:47,260 --> 00:12:53,800 if I make it nil we get an error unexpectedly found nil while unwrapping an optional value. 200 00:12:54,040 --> 00:13:02,050 So unless you are one million percent sure do not implicitly unwrap optionals this is kind of a last 201 00:13:02,050 --> 00:13:02,680 ditch thing. 202 00:13:02,680 --> 00:13:07,660 It's kind of if you have to if you're not 100 percent sure that there's a value do not force on rap 203 00:13:07,690 --> 00:13:12,440 or implicitly unwrap values like that OK it's not good practice. 204 00:13:12,460 --> 00:13:12,720 OK. 205 00:13:12,730 --> 00:13:17,500 So next up there's kind of a really cool thing I want to show you with optionals called nyl coalescing 206 00:13:18,040 --> 00:13:21,100 and something called using the ternary operator. 207 00:13:21,100 --> 00:13:30,990 So let's go ahead and call nyl coalescing and using turn every operator. 208 00:13:31,030 --> 00:13:39,340 So we're going to create an optional integer k so go ahead and type let optional end of type int equals 209 00:13:39,610 --> 00:13:47,230 nil and you'll see if we do this it's going to not let us it'll say we can't use nil on something of 210 00:13:47,230 --> 00:13:49,890 type int because nil is not an integer value. 211 00:13:49,990 --> 00:13:55,840 But if we set it to be an optional that means that we basically put that in a box and we say OK the 212 00:13:55,840 --> 00:14:02,860 box can have an nil value or it can have a numerical value so that's cool and all but what if we want 213 00:14:02,860 --> 00:14:07,890 to create a variable but we're not sure if optional int is going to have a value or not. 214 00:14:07,890 --> 00:14:14,800 Maybe we're pulling data from a server so we can say let results equals and watch what we can do. 215 00:14:14,920 --> 00:14:21,930 We can say it equals the optional and but what if you're not sure now if it comes back with value like 216 00:14:21,930 --> 00:14:27,630 if we gave it the value of five that's great and now optional is equal to five therefore result is equal 217 00:14:27,630 --> 00:14:28,450 to five. 218 00:14:28,530 --> 00:14:33,270 But if it comes back nil we might not want to set it to be nil right. 219 00:14:33,270 --> 00:14:35,420 That would cause a crash in our application. 220 00:14:35,430 --> 00:14:40,320 So what we can do is we can use the turn every operator by doing to question marks. 221 00:14:40,470 --> 00:14:42,610 Then after that we can type is zero. 222 00:14:42,720 --> 00:14:49,260 And what this is basically saying and you'll see it as it prints out is if we don't get a value set 223 00:14:49,260 --> 00:14:50,090 it to zero. 224 00:14:50,250 --> 00:14:52,000 Otherwise set it to be optional. 225 00:14:52,000 --> 00:14:54,850 And so this is kind of like like else. 226 00:14:55,020 --> 00:14:55,290 Think. 227 00:14:55,290 --> 00:14:58,180 Think of it like this optional it has a value. 228 00:14:58,260 --> 00:15:00,230 Let results equal optional. 229 00:15:00,250 --> 00:15:03,670 And if there's a value otherwise set it to be zero. 230 00:15:03,720 --> 00:15:07,590 Meaning if Neal comes through it's going to set it to zero just like you can see. 231 00:15:07,740 --> 00:15:13,050 Now if I set it to five you'll see that the optional and will print out as 5 because it has a value. 232 00:15:13,050 --> 00:15:14,830 Really really cool. 233 00:15:14,850 --> 00:15:19,790 So let's go and set it to nil just because it's pretty cool that it's using the ternary operator there. 234 00:15:20,140 --> 00:15:26,130 And last but not least we're going to go ahead and use a real world example with Comic-Con. 235 00:15:26,130 --> 00:15:28,830 I'm going to Comic-Con next month and I'm really excited. 236 00:15:28,830 --> 00:15:33,060 So I was thinking about it and thought it was a perfect example for what we're going to do. 237 00:15:33,060 --> 00:15:38,760 So first of all we need to create a class for Comic-Con attendee and we need to create a class for their 238 00:15:38,760 --> 00:15:42,200 admission badge so go ahead and type class. 239 00:15:42,550 --> 00:15:53,250 Comic-Con attendee K and we need a variable we need an admission badge like so of type admission badge 240 00:15:54,000 --> 00:15:58,920 which Thats a class will create in a second but we're going to make it optional because everybody who 241 00:15:58,920 --> 00:16:03,660 goes to Comic-Con they might not have a badge from the very beginning they might want to buy tickets 242 00:16:03,660 --> 00:16:04,600 when they get there. 243 00:16:04,890 --> 00:16:11,820 So we need to create a quick initialiser and we're just going to say badge of type admission badge and 244 00:16:11,850 --> 00:16:17,760 that of course is optional because they may or may not have a badge and we'll just say self admission 245 00:16:17,760 --> 00:16:22,080 badge is equal to badge just like that. 246 00:16:22,320 --> 00:16:27,350 OK so now we're going to create the admission badge class so that our attendees can actually attend. 247 00:16:27,350 --> 00:16:28,380 That would be helpful. 248 00:16:28,550 --> 00:16:37,370 So type class admission badge and let's go ahead and just say for Comic-Con we're just going to give 249 00:16:37,490 --> 00:16:39,740 a variable number of days. 250 00:16:39,740 --> 00:16:41,700 That's usually how Comic-Con tickets go. 251 00:16:41,990 --> 00:16:47,690 And every bag is going to have an explicit value so we don't need to make it optional and we just need 252 00:16:47,690 --> 00:16:48,700 to initialize it. 253 00:16:48,710 --> 00:16:58,160 So go ahead and type number of days of type int and we'll set self number of days to be equal to number 254 00:16:58,160 --> 00:16:59,240 of days. 255 00:16:59,240 --> 00:17:00,190 Very cool. 256 00:17:00,500 --> 00:17:04,200 So what we're going to do is we're going to create an admission badge. 257 00:17:04,250 --> 00:17:09,470 We're going to create a Comic-Con attendee and we're going to give them that admission badge so go ahead 258 00:17:09,470 --> 00:17:15,780 and type let admission badge equals admission badge and we're going to pass in a number of days. 259 00:17:15,800 --> 00:17:20,660 Let's just give them a three day pass and now we're going to create a Comic-Con attendee. 260 00:17:20,660 --> 00:17:27,950 So let attendee equals Comic-Con attendee and Wiens to give them a badge so go ahead and pass in the 261 00:17:27,950 --> 00:17:29,230 admission badge. 262 00:17:29,630 --> 00:17:35,350 And just like that we have an admission badge and we have a Comic-Con attendee which is really cool. 263 00:17:35,540 --> 00:17:40,220 But what if I was building an app where I wanted to show how many days left you have on your Comic-Con 264 00:17:40,220 --> 00:17:50,090 badge I might type something like this if let days a tenable meaning I have X amount of days left. 265 00:17:50,210 --> 00:17:58,100 We can check that by going in to attend the admission badge end did you notice admission badge is optional. 266 00:17:58,120 --> 00:18:03,130 You can see that right there and watch what happens when I type that number of days. 267 00:18:03,190 --> 00:18:06,170 That's because I might not have an admission badge. 268 00:18:06,220 --> 00:18:06,690 OK. 269 00:18:06,790 --> 00:18:11,860 So it's putting an optional there so that it is safely unwrapping and safely using the value in my admission 270 00:18:11,860 --> 00:18:13,230 badge. 271 00:18:13,570 --> 00:18:19,180 So if days amendable is equal to number of days which in this case is three we're going to go ahead 272 00:18:19,210 --> 00:18:22,440 and print whips. 273 00:18:22,600 --> 00:18:33,640 We're going to print this tente can enter Comic-Con for we're going to print the number of days here 274 00:18:35,020 --> 00:18:37,440 days a tenable days. 275 00:18:37,730 --> 00:18:41,860 Else we're going to print something else. 276 00:18:41,860 --> 00:18:48,970 Now we didn't think what would we print if days attend the is not equal or if days a tenable number 277 00:18:48,970 --> 00:18:50,840 of days comes back as nil. 278 00:18:51,040 --> 00:18:57,320 We need to say this person has not yet purchased a ticket. 279 00:18:57,430 --> 00:19:04,290 Please refer them to the ticketing window and watch what happens when we print this out. 280 00:19:04,360 --> 00:19:04,640 OK. 281 00:19:04,660 --> 00:19:08,380 So it says this attendee can enter Comic-Con for three days. 282 00:19:08,590 --> 00:19:15,160 But watch what happens if I remove the admission badge remember for a Comic-Con attendee admission badge 283 00:19:15,220 --> 00:19:17,780 is optional so I can pass in Knill. 284 00:19:17,980 --> 00:19:21,090 What if I did not have an admission badge. 285 00:19:21,310 --> 00:19:22,690 If it comes in as nil. 286 00:19:22,690 --> 00:19:24,050 Watch what happens. 287 00:19:24,070 --> 00:19:26,080 This person has not yet purchased a ticket. 288 00:19:26,080 --> 00:19:33,730 Please refer them to the ticketing window because I was using optional binding and that basically created 289 00:19:33,730 --> 00:19:39,370 a constant here called days attend table and I set it to be equal to the number of days from the admission 290 00:19:39,370 --> 00:19:40,070 badge. 291 00:19:40,090 --> 00:19:45,980 But if the admission badge is nil then I get an optional value of nil and it prints out here. 292 00:19:46,000 --> 00:19:48,330 This person has not yet purchased the ticket. 293 00:19:48,340 --> 00:19:51,820 This is called Let me put it up here at the very top. 294 00:19:51,850 --> 00:19:58,810 This is called optional chaining and it allows us to change values of optionals together so that we 295 00:19:58,810 --> 00:20:05,120 can get a value or handle errors when it returns nil optionals are incredibly helpful. 296 00:20:05,200 --> 00:20:11,270 I really hope that you can see that these are just some super helpful small examples of using optionals. 297 00:20:11,440 --> 00:20:15,790 And of course if you're confused or if you want to know more I would highly recommend digging into the 298 00:20:15,790 --> 00:20:16,780 Apple documentation. 299 00:20:16,780 --> 00:20:18,720 There are tons of examples there. 300 00:20:18,850 --> 00:20:20,710 So amazing work with this video. 301 00:20:20,710 --> 00:20:22,380 And let's head over to the next one.