1 00:00:03,390 --> 00:00:12,440 Hey Jack is here with themselves to welcome you back for part two of our journey into protocol oriented 2 00:00:12,440 --> 00:00:13,280 programming. 3 00:00:14,560 --> 00:00:20,220 In the last lesson we talked about the difference between reference and value types or classes versus 4 00:00:20,220 --> 00:00:21,780 structures. 5 00:00:21,780 --> 00:00:29,700 One of the limitations that you tap taps have had in the past is that I do not offer inheritance with 6 00:00:29,700 --> 00:00:30,840 classes in swift. 7 00:00:30,840 --> 00:00:33,140 We have single inheritance. 8 00:00:33,300 --> 00:00:38,400 This means that we can implement functionality in a superclass and then use that functionality in our 9 00:00:38,400 --> 00:00:40,240 subclasses. 10 00:00:40,260 --> 00:00:46,470 Some languages offer multiple inherit inheritance where classes can have more than one superclass but 11 00:00:46,470 --> 00:00:53,960 in swift we're limited to exactly one superclass the inheritance problem with value types has virtually 12 00:00:53,960 --> 00:00:54,710 been eliminated. 13 00:00:54,710 --> 00:01:02,650 With the advent of protocols and protocol extensions protocols are kind of like contracts or blueprints. 14 00:01:02,870 --> 00:01:09,140 They define what functionality a class or structure are all for but they do not provide any implementation 15 00:01:09,140 --> 00:01:09,920 code. 16 00:01:09,980 --> 00:01:16,010 They simply define requirements for types that conform to that protocol. 17 00:01:16,010 --> 00:01:22,950 Some other languages offer a similar feature namely interfaces with protocol extensions you can now 18 00:01:22,970 --> 00:01:30,110 extend those protocols and any types that conform to them and actually provide common functionality. 19 00:01:30,110 --> 00:01:35,420 This functionality or implementation code can be functions or computed properties. 20 00:01:35,420 --> 00:01:40,790 Note here that properties must be computed values cannot be assigned directly to properties of protocol 21 00:01:40,790 --> 00:01:42,240 extensions. 22 00:01:42,470 --> 00:01:47,750 In this lesson we're going to go through a playground project and take a look at protocols and the next 23 00:01:47,750 --> 00:01:54,410 list will add and protocol extensions and finally we'll briefly cover generics before we move on to 24 00:01:54,410 --> 00:02:00,920 some real world examples of ways to incorporate protocol into programming into your everyday code. 25 00:02:01,770 --> 00:02:04,400 So I was going to pull up a new playground here. 26 00:02:05,410 --> 00:02:11,100 To get started and we'll just call this protocol's 27 00:02:13,620 --> 00:02:16,800 and we'll leave it is our way saying we'll save it on the desktop 28 00:02:19,630 --> 00:02:24,040 or get rid of that line there. 29 00:02:24,080 --> 00:02:34,020 Now the first thing we're going to do is we'll go ahead and create a protocol for a vehicle. 30 00:02:34,070 --> 00:02:40,220 So in this instance we could do if we were modeling using reference types or classes we could have a 31 00:02:40,220 --> 00:02:47,360 base class that was a vehicle and we could extend that to subclasses in the form of more specialized 32 00:02:47,870 --> 00:02:49,080 classes. 33 00:02:49,130 --> 00:02:53,020 In this case this is all about protocol so that's what we're going to do here. 34 00:02:53,450 --> 00:02:54,880 So. 35 00:02:55,310 --> 00:03:02,810 So define a protocol of vehicle and we're going to have a property here for it and we'll just call it 36 00:03:03,110 --> 00:03:12,980 is running and we'll make that a boolean and in protocol's you define whether it's Read-Only property 37 00:03:13,460 --> 00:03:15,070 or reroute property. 38 00:03:15,290 --> 00:03:23,210 In this particular protocol's going to be a read write property so we've got to specify get set there. 39 00:03:24,160 --> 00:03:26,970 All right. 40 00:03:27,800 --> 00:03:33,320 Now we're going to have a couple of functions in here and since we might be using this with a structure 41 00:03:33,980 --> 00:03:36,680 there's one little caveat here. 42 00:03:36,680 --> 00:03:43,100 When you define a function in a protocol so we're going to say thanks start. 43 00:03:43,130 --> 00:03:44,660 And this is just going to be a function. 44 00:03:44,670 --> 00:03:50,870 Again these are just blueprints or contracts and whatever conforms to it has to implement these functions 45 00:03:50,870 --> 00:03:52,960 in their body. 46 00:03:53,180 --> 00:04:01,530 So we're going to have a start function and we're also going to have a turn or function. 47 00:04:01,550 --> 00:04:06,410 The caveat here is if you use these with value types you have to specify 48 00:04:09,650 --> 00:04:12,300 mutating in front of the function. 49 00:04:12,470 --> 00:04:21,440 If it's going to mutate a property inside the structure or a value top that is going to conform to this 50 00:04:21,910 --> 00:04:24,380 so we'll go ahead and add that in here. 51 00:04:24,980 --> 00:04:30,260 All you need to know is if you're going to use structures with this and you're going to have functions 52 00:04:30,260 --> 00:04:35,460 that modify internal properties and you have to put that mutating keyword in there. 53 00:04:35,540 --> 00:04:37,300 So this is just Luxa. 54 00:04:37,310 --> 00:04:44,720 This is a real simple example but we've got our vehicle protocol here and everyone go ahead and create 55 00:04:44,720 --> 00:04:50,690 a sports car that is going to conform to the vehicle protocol and the sports car is going to be a struct 56 00:04:50,840 --> 00:04:56,210 so we'll use a value top here. 57 00:04:56,920 --> 00:04:57,600 All right. 58 00:04:57,730 --> 00:05:05,390 And then now we've got data since it conforms to vehicle you'll see here the error it says top sports 59 00:05:05,390 --> 00:05:07,940 car does not conform to a protocol vehicle. 60 00:05:08,300 --> 00:05:14,990 Well that's because we haven't implemented any of those required properties or method yet. 61 00:05:14,990 --> 00:05:17,000 So now we need to go in here in 62 00:05:20,590 --> 00:05:25,890 specify our properties so we're going to set this one the false by default. 63 00:05:26,640 --> 00:05:29,150 And now we've got to do our functions. 64 00:05:29,350 --> 00:05:37,910 So this being a structure we need the mutating keyword and you'll notice there that it can. 65 00:05:38,140 --> 00:05:41,790 Since we're conforming to that topic kind of feel some of that for you. 66 00:05:42,340 --> 00:05:48,450 So in the Star function we're just going to say it is running. 67 00:05:49,120 --> 00:05:51,640 So if it's already running we're just going to print it 68 00:05:54,730 --> 00:05:57,430 already started. 69 00:05:57,430 --> 00:06:04,210 Otherwise we're going to say is running equals true. 70 00:06:04,230 --> 00:06:05,590 In the end we're going to present 71 00:06:08,840 --> 00:06:10,580 room. 72 00:06:10,700 --> 00:06:12,980 Think that's kind of how sports car sales are. 73 00:06:13,240 --> 00:06:14,800 12 Hardeen. 74 00:06:15,450 --> 00:06:25,380 All right now we've got another function here that we have to implement and this one is all. 75 00:06:26,430 --> 00:06:36,560 So we're going to say it is running and we're going to say is running equals false and we're going to 76 00:06:36,570 --> 00:06:40,550 preempt crickets. 77 00:06:40,610 --> 00:06:41,530 I have no idea. 78 00:06:41,540 --> 00:06:43,880 It's just. 79 00:06:44,360 --> 00:06:48,100 Otherwise we're going to say prent. 80 00:06:48,220 --> 00:06:50,810 I already did. 81 00:06:52,360 --> 00:06:53,030 OK. 82 00:06:53,270 --> 00:06:56,710 So we've got our is running property here. 83 00:06:56,990 --> 00:07:00,340 We've got our start function in our turn off function. 84 00:07:00,460 --> 00:07:03,310 And you'll notice here that we've lost our error. 85 00:07:03,380 --> 00:07:10,190 So now we conform to the vehicle protocol now that we've implemented all of those properties and methods 86 00:07:11,780 --> 00:07:14,050 and protocols. 87 00:07:14,810 --> 00:07:20,870 Any any type can conform to a protocol so it doesn't have to be a value type it can be a reference type. 88 00:07:20,960 --> 00:07:29,330 So just to prove this we'll go ahead Mike our next one a class so we'll say a semi truck and we'll conform 89 00:07:29,330 --> 00:07:32,210 to the vehicle protocol. 90 00:07:32,900 --> 00:07:34,900 And again you'll see here we get our error. 91 00:07:34,910 --> 00:07:36,310 It does not conform. 92 00:07:36,650 --> 00:07:47,310 So now we need to add in our property and we'll say false to begin with we make a little bit more space 93 00:07:47,310 --> 00:07:47,830 here. 94 00:07:50,690 --> 00:07:50,950 All right. 95 00:07:50,960 --> 00:07:56,990 Now this is a class so the mutating keyword is not required here. 96 00:07:58,440 --> 00:08:03,150 Made a reference tot the properties in here are immutable. 97 00:08:03,240 --> 00:08:10,410 We don't need the mutating key word and it doesn't hurt that it's seeing that it's in the protocol declaration 98 00:08:10,770 --> 00:08:17,630 that is just in case you use it in a structure then you're able to modify your properties. 99 00:08:17,760 --> 00:08:30,120 So in the class we're just going to say phunk start and we're going to say if it is running roadside 100 00:08:30,130 --> 00:08:30,820 print 101 00:08:34,070 --> 00:08:37,620 already started. 102 00:08:37,620 --> 00:08:46,740 Otherwise we're going to say is running is true and we're going to present. 103 00:08:47,400 --> 00:08:50,700 I don't know how does an 18 wheeler sound rumble. 104 00:08:50,940 --> 00:08:53,460 Maybe that's a good word for it. 105 00:08:53,460 --> 00:08:53,830 All right. 106 00:08:53,840 --> 00:08:57,330 So we've got to turn our star functionality or turn off function 107 00:09:00,150 --> 00:09:08,340 so we'll say if it is running and we're going to kill it here so we'll say is running equals false hopes 108 00:09:09,900 --> 00:09:11,510 and we'll say Brant 109 00:09:15,160 --> 00:09:17,140 I don't know. 110 00:09:17,640 --> 00:09:19,560 Silence. 111 00:09:22,770 --> 00:09:27,740 And then if it's not running we'll say 112 00:09:30,580 --> 00:09:36,790 already shut down I guess. 113 00:09:36,860 --> 00:09:38,610 All right. 114 00:09:39,030 --> 00:09:42,660 So hopefully you need those if else is backwards. 115 00:09:42,700 --> 00:09:45,840 But OK now the end. 116 00:09:46,330 --> 00:09:53,890 You can also just because you conform to that vehicle protocol you can still add other functionality 117 00:09:53,890 --> 00:09:54,610 in here. 118 00:09:54,940 --> 00:09:59,650 So let's say in the case of the 18 wheeler we want to add another function 119 00:10:02,520 --> 00:10:07,330 called blow air horn. 120 00:10:07,330 --> 00:10:14,900 If I can type and we're just going to preach it how does an air horn sound. 121 00:10:18,950 --> 00:10:20,960 What is a tune. 122 00:10:20,970 --> 00:10:22,630 All right. 123 00:10:23,530 --> 00:10:29,760 So now we've got our semi truck class which conforms to vehicle and we've got our sports car struck 124 00:10:29,770 --> 00:10:32,980 that conforms to vehicle. 125 00:10:33,040 --> 00:10:34,350 So let's move on down. 126 00:10:34,360 --> 00:10:37,200 Let's go and create some instances here. 127 00:10:37,840 --> 00:10:53,120 So we'll say car one is equal to a sports car and say truck one is a call to a semi truck. 128 00:10:53,410 --> 00:10:53,890 All right. 129 00:10:53,900 --> 00:10:57,450 Now we can do car want to start. 130 00:10:58,070 --> 00:10:59,810 We can do truck one 131 00:11:02,950 --> 00:11:12,280 star and we can say truck one blow and we pull up our console down here. 132 00:11:12,290 --> 00:11:14,280 You can see that we're putting these things out. 133 00:11:16,190 --> 00:11:21,110 So we've successfully conformed to that protocol. 134 00:11:21,780 --> 00:11:27,880 And the real power with protocols coming in with protocol extensions are a lot of the power. 135 00:11:27,900 --> 00:11:29,930 And we'll go over that in the next lesson. 136 00:11:30,090 --> 00:11:40,360 But one really cool thing about this let's go ahead and turn these off. 137 00:11:40,900 --> 00:11:43,580 So we've got them both shut down. 138 00:11:43,660 --> 00:11:51,460 One really cool thing about this is we can do something like we can make a vehicle array and we'll just 139 00:11:52,030 --> 00:11:59,710 instead of using the brackets syntax we'll use this the bracket syntax is actually an alternative syntax. 140 00:11:59,860 --> 00:12:03,130 This right here is actually house defined in the standard library. 141 00:12:03,700 --> 00:12:13,090 And for the tab we're going to make it a vehicle top so we're going to put in here car one and truck 142 00:12:13,090 --> 00:12:16,820 one. 143 00:12:17,000 --> 00:12:22,490 So now we've got an array even though these are two different types. 144 00:12:22,500 --> 00:12:24,950 One is a sports car and one's of Sumatra. 145 00:12:25,160 --> 00:12:29,450 They're in the same right because they both conform to vehicle. 146 00:12:29,930 --> 00:12:33,210 So you can use protocols as tops. 147 00:12:33,300 --> 00:12:35,480 This in this situation. 148 00:12:35,660 --> 00:12:37,550 And then if we go ahead and walk through them 149 00:13:02,170 --> 00:13:04,760 we'll just print out the vehicle. 150 00:13:04,760 --> 00:13:10,820 So now you can see down here we've got a sports car and it's got the is running is false and we just 151 00:13:10,820 --> 00:13:12,290 got a semi truck. 152 00:13:12,590 --> 00:13:18,670 So they're not there's no standard description here that's printed out. 153 00:13:18,770 --> 00:13:21,130 What kind of going to that here in just a second. 154 00:13:21,650 --> 00:13:24,830 But if I try to do something like vehicle dot 155 00:13:30,200 --> 00:13:40,830 blow air horn I get an error here because the top vehicle has no memory blower horn. 156 00:13:40,850 --> 00:13:48,140 So basically we could use any of these things that we define our protocol but we extended our Sumatra 157 00:13:48,230 --> 00:13:50,180 and added this blower horn function. 158 00:13:50,180 --> 00:13:50,810 Right. 159 00:13:51,940 --> 00:13:57,230 So this being a top vehicle it knows nothing about blower horn. 160 00:13:57,430 --> 00:14:00,990 If we wanted to use this in this array as we walk it. 161 00:14:01,150 --> 00:14:12,750 So if we did something like gef let the cool cool be cool as a semi truck then we can say we call it 162 00:14:12,980 --> 00:14:15,120 blow air horn. 163 00:14:15,460 --> 00:14:17,140 Now you can see down here in the car. 164 00:14:17,150 --> 00:14:20,210 So we get to blow air horn. 165 00:14:20,320 --> 00:14:26,830 So basically we look through this right car was not a semi truck so it skipped over the next element 166 00:14:26,830 --> 00:14:30,810 was truck and it blew it blew the air horn. 167 00:14:30,830 --> 00:14:32,000 So that's pretty cool. 168 00:14:34,380 --> 00:14:38,750 In addition to that protocols can be combined. 169 00:14:39,360 --> 00:14:49,100 So there is a protocol called custom screen convertible that a lot of types conform to. 170 00:14:49,920 --> 00:14:53,130 And I'm going to editing it here. 171 00:14:53,130 --> 00:14:56,110 Click on it and we'll go look at the implementation. 172 00:14:57,260 --> 00:15:02,540 So you say here this is a protocol custom inconvertible what's in the standard library and it gives 173 00:15:02,540 --> 00:15:05,300 a textual representation of the instance. 174 00:15:05,510 --> 00:15:10,760 And basically when you conform to this you have to add this property here description and it's just 175 00:15:10,760 --> 00:15:12,410 a good property. 176 00:15:12,440 --> 00:15:19,780 And so whenever you call the description on your object you give it a friendly name to print out or 177 00:15:19,810 --> 00:15:21,040 to return. 178 00:15:21,560 --> 00:15:24,620 So let's go back and let's implement this. 179 00:15:24,620 --> 00:15:31,080 So this protocol is in the standard library so we're just going to add it to our vehicle protocol here 180 00:15:31,290 --> 00:15:38,970 in the way you do that is sort of how you either conform to the protocol or you inherit from a superclass. 181 00:15:38,970 --> 00:15:43,260 So you just put your colon here and then we add custom string convertible. 182 00:15:43,480 --> 00:15:49,050 And now we're getting in the air here because it does not conform to it. 183 00:15:49,180 --> 00:15:50,500 So now we need to add 184 00:15:53,480 --> 00:15:54,360 description. 185 00:15:54,420 --> 00:16:00,810 So we need to add description into our sports car and this is we're going to return 186 00:16:04,440 --> 00:16:05,680 we'll see 187 00:16:12,010 --> 00:16:14,130 yeah let's do it this way. 188 00:16:14,340 --> 00:16:21,810 So we'll say if it is running we'll present sports car 189 00:16:24,060 --> 00:16:26,120 currently running. 190 00:16:26,790 --> 00:16:27,690 Otherwise 191 00:16:30,360 --> 00:16:36,580 we'll present. 192 00:16:37,380 --> 00:16:40,890 And then we'll do the same thing down here in Sumatra. 193 00:16:41,310 --> 00:16:45,450 And you say we don't have to specify because some steering convertible here because we specified it 194 00:16:46,230 --> 00:16:48,040 in our vehicle protocol. 195 00:16:48,570 --> 00:16:56,910 Now we could take this out and add it. 196 00:16:57,040 --> 00:16:59,240 Let's see we implemented it here. 197 00:16:59,240 --> 00:17:04,190 So so now we're getting this error on this description property here we could just put a comma in the 198 00:17:04,220 --> 00:17:28,140 custom string convertible. 199 00:17:28,200 --> 00:17:32,030 Sorry we don't need a print here. 200 00:17:32,040 --> 00:17:33,010 Wanting a return 201 00:17:42,150 --> 00:17:44,060 are sort of taken care of. 202 00:17:46,920 --> 00:17:47,360 All right. 203 00:17:47,420 --> 00:17:48,900 So their goals are. 204 00:17:49,340 --> 00:17:49,960 So now the 205 00:17:52,890 --> 00:17:59,160 now that we've got that now we've got it in the sports car that functionality that we don't have in 206 00:17:59,160 --> 00:18:00,000 Sumatra. 207 00:18:01,220 --> 00:18:07,220 And then again if we wanted to make it available to every vehicle we just go ahead and put it back in 208 00:18:07,220 --> 00:18:17,930 our protocol peer when we do that we see right here that need implemented in our in our semi truck as 209 00:18:17,930 --> 00:18:18,230 well. 210 00:18:18,230 --> 00:18:36,010 So if it is running and we need to return not pregnant or semi truck currently running otherwise it 211 00:18:36,510 --> 00:18:42,630 turns Sumatra currently shut down. 212 00:18:44,720 --> 00:18:45,320 OK. 213 00:18:45,400 --> 00:18:46,420 And that takes care of that. 214 00:18:46,420 --> 00:18:50,980 So now the when we loop through this we'll take this code out of here. 215 00:18:53,210 --> 00:18:59,450 We'll just come back we'll look through and we'll print the vehicle description because it's tied in 216 00:18:59,460 --> 00:19:02,270 with both of them now so we'll say 217 00:19:06,600 --> 00:19:07,350 print 218 00:19:13,040 --> 00:19:16,390 the vehicle description. 219 00:19:16,560 --> 00:19:22,480 And so now down here in the car so you can see we've got a sports car currently turned off in a semi 220 00:19:22,480 --> 00:19:24,610 truck currently shut down. 221 00:19:25,480 --> 00:19:31,710 So now if we come up here we've got them both turned off if we just take these out. 222 00:19:31,900 --> 00:19:32,730 They should change it. 223 00:19:32,730 --> 00:19:38,510 Now you can say our sports car is currently running in semi truck is currently running so we could just 224 00:19:38,510 --> 00:19:40,150 shut one of them down. 225 00:19:42,730 --> 00:19:45,170 So we could turn off truck one. 226 00:19:45,260 --> 00:19:48,140 Now you can see our semi trucks currently shut down. 227 00:19:48,910 --> 00:19:55,660 So that kind of covers protocols in how you can form to them you still have to provide all the implementation 228 00:19:55,660 --> 00:19:56,410 code. 229 00:19:56,800 --> 00:20:02,830 And like I said that's where the magic happens is when you start doing protocol extensions you can actually 230 00:20:02,830 --> 00:20:05,120 provide some of that implementation. 231 00:20:05,120 --> 00:20:07,500 And I'll talk about why the next lesson. 232 00:20:07,750 --> 00:20:15,110 But that's our introduction to protocols and we'll continue to put it together in the next lesson. 233 00:20:15,130 --> 00:20:16,310 Thanks for watching. 234 00:20:16,450 --> 00:20:17,900 We'll see you next time. 235 00:20:17,920 --> 00:20:18,120 Ligers.