1 00:00:04,150 --> 00:00:10,790 Hey Dave is here with Fobes dot com and I'd like to welcome you back part three of our journey into 2 00:00:10,800 --> 00:00:12,720 procol programming. 3 00:00:13,340 --> 00:00:18,900 And the last lesson we've covered the basics of protocols and this list and we're going to dive into 4 00:00:18,900 --> 00:00:20,480 protocol extensions. 5 00:00:20,880 --> 00:00:25,990 And as I said previously protocol extensions are where the magic happens. 6 00:00:26,160 --> 00:00:29,660 You can extend any protocol to give them functionality. 7 00:00:29,730 --> 00:00:35,130 This means that you can not only exchange your own protocols but any protocol from a standard library 8 00:00:35,130 --> 00:00:42,310 is well protocol extensions were introduced as a way around some of the limitations of working with 9 00:00:42,310 --> 00:00:45,700 value types which offer no inheritance. 10 00:00:45,700 --> 00:00:51,340 Now you can place implementation code in an extension and it's available to any class or stroke that 11 00:00:51,340 --> 00:00:52,970 conforms to that protocol. 12 00:00:54,230 --> 00:01:00,890 So without any further ado let's go ahead and get started and we'll dive back in where we left off in 13 00:01:00,890 --> 00:01:02,900 the last listen. 14 00:01:02,940 --> 00:01:08,270 So I've got my playground open here that we had open in the last lesson that we were playing with. 15 00:01:08,490 --> 00:01:16,830 If you remember we did a vehicle protocol and then we create a sports car strapped and a semi truck 16 00:01:16,830 --> 00:01:25,250 strapped and we create instances of those and then we start on blue the air horn turned them off. 17 00:01:25,250 --> 00:01:26,830 So for. 18 00:01:27,010 --> 00:01:30,940 So we're going to extend or we're going use procol extensions today. 19 00:01:31,800 --> 00:01:36,290 To try to explain them to you and let you see the power that I have. 20 00:01:37,270 --> 00:01:45,250 Now this is just a kind of introductory lesson in protocols and protocols protocol extensions so they 21 00:01:45,250 --> 00:01:47,190 get really complicated. 22 00:01:47,770 --> 00:01:51,290 But there's a lot of power there and they're really nice. 23 00:01:51,330 --> 00:01:58,880 So we're just going to kind of go over the basics here so you kind of get an idea of what's going on. 24 00:01:59,960 --> 00:02:09,620 So in our vehicle protocol here we've got our is running low in property and we've got these two mutating 25 00:02:09,620 --> 00:02:10,700 Funk's here. 26 00:02:11,060 --> 00:02:15,680 I want to go ahead and add and make 27 00:02:24,810 --> 00:02:35,440 when I up making a model for our vehicles. 28 00:02:36,380 --> 00:02:45,110 And then we're going to go ahead and create our extension right here and we'll just do extension vehicle 29 00:02:46,130 --> 00:02:47,570 and that's really all there is to it. 30 00:02:47,570 --> 00:02:51,110 As far as declaring the extension 31 00:02:54,570 --> 00:02:56,730 of course we're getting these errors here. 32 00:02:58,950 --> 00:03:01,670 So this is mostly the model. 33 00:03:01,680 --> 00:03:03,170 There we go. 34 00:03:03,430 --> 00:03:09,280 We're getting errors here that this doesn't conform any more because we've added these two properties 35 00:03:09,280 --> 00:03:09,780 here. 36 00:03:10,740 --> 00:03:17,020 So let's run down and add those into our sports core 37 00:03:26,020 --> 00:03:27,640 sports car Astra. 38 00:03:27,840 --> 00:03:34,520 So where did we go down here to our semi truck it's a class. 39 00:03:34,620 --> 00:03:44,390 Watch what happens when I add these two properties. 40 00:03:44,710 --> 00:03:49,630 An error now an error says that there is no initializers. 41 00:03:50,260 --> 00:03:55,960 And what's going on here in this is running we gave it a default value of false. 42 00:03:55,960 --> 00:04:00,980 So when there was no initialiser it didn't complain because it had a value on these two. 43 00:04:00,990 --> 00:04:04,440 We don't have a value so we're going to have to provide an initialiser. 44 00:04:05,080 --> 00:04:06,880 So we'll do it 45 00:04:21,450 --> 00:04:25,140 and then we'll just set the set of properties up here. 46 00:04:38,610 --> 00:04:44,640 Mo okay and that should have taken care of here. 47 00:04:45,720 --> 00:04:50,770 Except now we're getting them down here because we have it we didn't declare these correctly. 48 00:04:51,010 --> 00:04:53,670 Avoid comment that out for just a minute. 49 00:04:53,670 --> 00:04:56,190 Actually we're going come in all this out for me. 50 00:04:58,160 --> 00:04:58,860 OK. 51 00:04:58,930 --> 00:05:04,130 So let's go back to our extension in here. 52 00:05:05,140 --> 00:05:08,780 I'm going to go ahead and change the way that we laid this out. 53 00:05:09,780 --> 00:05:17,850 So if you say we've got duplicated code then we've got a set of start and turn off method in both of 54 00:05:17,850 --> 00:05:19,770 these types here. 55 00:05:21,290 --> 00:05:30,320 So what I'm going to do is we're going to say mutating from store to 56 00:05:33,260 --> 00:05:37,760 in mutating. 57 00:05:38,030 --> 00:05:42,110 Turn off. 58 00:05:42,630 --> 00:05:43,400 All right. 59 00:05:43,590 --> 00:05:48,160 Now the end in these methods here we're going to check. 60 00:05:48,200 --> 00:05:56,220 So for the start we're going to say if is running just like we did before and if it is we will say present 61 00:05:56,490 --> 00:05:57,680 already started 62 00:06:02,530 --> 00:06:11,590 otherwise we're going to say is running Google's true and we're going to print. 63 00:06:12,160 --> 00:06:16,390 We're going to print the descriptions so 64 00:06:23,830 --> 00:06:27,400 so self description and then fired up. 65 00:06:27,420 --> 00:06:37,130 If you'll remember we added this custom string convertible here which gave us that description property. 66 00:06:37,160 --> 00:06:42,470 All right so now let's go ahead and implement our turn off function. 67 00:06:42,500 --> 00:06:49,340 It's all safe is running do is running is false. 68 00:06:49,390 --> 00:07:00,460 Print it and we'll do the same thing here we'll do self description and shit. 69 00:07:01,670 --> 00:07:06,620 And the reason we're doing this is because we're implementing this in this extension and bought the 70 00:07:06,620 --> 00:07:12,790 sports car and a semi truck are going to get these methods because we're implementing it in the extension. 71 00:07:12,890 --> 00:07:23,730 So basically we need to pull these out of here and just delete those. 72 00:07:24,920 --> 00:07:29,970 And again instructs require mutating functions classes don't. 73 00:07:30,230 --> 00:07:33,750 So we added the mutating key word here. 74 00:07:34,060 --> 00:07:39,650 But even though we've it's available in a in a class it it doesn't matter it just ignores that mutating 75 00:07:39,690 --> 00:07:40,730 keyword. 76 00:07:41,310 --> 00:07:42,740 All right. 77 00:07:44,770 --> 00:07:46,290 Where are we at here. 78 00:07:48,140 --> 00:07:49,960 Are backing our extinction. 79 00:07:53,120 --> 00:07:56,420 Say I put the else statement in here to know 80 00:08:14,600 --> 00:08:15,660 OK. 81 00:08:16,170 --> 00:08:20,820 So now we've got our turn off and start functions here and they're implemented. 82 00:08:20,820 --> 00:08:26,730 So sports car and semi truck are going to get those automatically because we conform to the vehicle 83 00:08:26,730 --> 00:08:28,050 protocol. 84 00:08:28,050 --> 00:08:32,850 Now I'm going to go in here and change up the description just a little bit and we're just going to 85 00:08:34,470 --> 00:08:36,200 return self 86 00:08:39,360 --> 00:08:41,640 self dot. 87 00:08:41,810 --> 00:08:43,490 See you on one second. 88 00:08:48,930 --> 00:08:51,770 Let you know actually let's do something different here. 89 00:08:52,840 --> 00:08:56,650 It was come back up here and let's say it's something else in our expansion. 90 00:08:56,730 --> 00:08:59,670 So let's add another property and we'll just call this make model 91 00:09:02,580 --> 00:09:04,520 and we'll just return 92 00:09:15,060 --> 00:09:21,330 we'll just return and make in a model that way whatever we get we'll just pass that in the description 93 00:09:21,330 --> 00:09:22,980 here. 94 00:09:25,890 --> 00:09:35,130 So we'll just for the description which is return self make model and then we'll do the same thing down 95 00:09:35,130 --> 00:09:47,250 here in the in the big league we'll just say return self to make model. 96 00:09:47,560 --> 00:09:48,120 All right. 97 00:09:50,450 --> 00:10:00,250 Now let's come back down here to where we declare these let's call it an and this and you'll see. 98 00:10:00,260 --> 00:10:07,130 Now I've got an auto complete suggestion what we need put there. 99 00:10:07,190 --> 00:10:13,720 So we've got is running and by default we're going to say false and make let's say this is this is a 100 00:10:13,720 --> 00:10:24,100 sports car so Porsche models say 9 11. 101 00:10:25,800 --> 00:10:30,780 The name will come semi truck here. 102 00:10:31,040 --> 00:10:33,970 We're getting the same thing not running. 103 00:10:34,340 --> 00:10:40,850 This is a Peter real and it's virago. 104 00:10:41,000 --> 00:10:44,360 I have no idea if that's a real truck or not but we're going to go with it. 105 00:10:45,610 --> 00:10:46,260 All right. 106 00:10:46,290 --> 00:10:48,960 In the end at that point let's go ahead and comment. 107 00:10:48,950 --> 00:11:00,580 These And so you see now are start methods are retired in the make and model and fired up make and model 108 00:11:00,580 --> 00:11:07,260 fired up and we still blow in the air horn because it's implemented just in a semi truck class 109 00:11:11,810 --> 00:11:13,120 and will turn off. 110 00:11:13,110 --> 00:11:15,420 And now the Peterbilt RAGO shut down 111 00:11:19,460 --> 00:11:28,650 and for here let's pretend we're cool dot make model. 112 00:11:28,680 --> 00:11:29,280 All right. 113 00:11:29,340 --> 00:11:36,060 So we can see here they are right now is putting out a Porsche 911 and appear before Argo. 114 00:11:36,390 --> 00:11:40,060 So that's kind of the power of that protocol extensions bring you. 115 00:11:40,350 --> 00:11:50,570 You can actually implement functions and computed properties in your extensions and then anything that 116 00:11:50,950 --> 00:11:58,530 that conforms to those two that protocol will automatically get that functionality. 117 00:11:58,530 --> 00:12:03,150 This is just kind of a brief overview of it but I think you could probably see the power 118 00:12:07,110 --> 00:12:14,140 so it's real similar to an extension of a type which if you'll recall 119 00:12:18,270 --> 00:12:24,480 let's just extend it double. 120 00:12:25,800 --> 00:12:30,200 So we're going to extend it and we're going to give it a dollar string. 121 00:12:31,020 --> 00:12:32,410 We're going to retire return 122 00:12:35,450 --> 00:12:45,470 string format and we're going to say a dollar sign and then we want to pad with zeros to places and 123 00:12:45,470 --> 00:12:47,510 we want to sell. 124 00:12:48,080 --> 00:12:49,550 So we've just extended a double here. 125 00:12:49,550 --> 00:12:55,700 Now this is a protocol extension this is a this is a top extension which you can do the same sort of 126 00:12:55,700 --> 00:13:02,510 thing any protocol that's in the standard library or any protocol that that you implement yourself. 127 00:13:02,510 --> 00:13:04,640 You can extend it in this way. 128 00:13:04,640 --> 00:13:12,620 So in this case right here we could say our per seat equals let's just say thirty two point one five 129 00:13:13,430 --> 00:13:22,680 times zero point one five Ok so we got four point eight two to five and we want to express that as a 130 00:13:22,680 --> 00:13:23,710 dollar. 131 00:13:24,210 --> 00:13:29,440 So all we've got to do now that we have that extension is percent dollar. 132 00:13:31,510 --> 00:13:32,290 And now you see 133 00:13:35,940 --> 00:13:45,390 I left out the Persius or so now you can see that just by adding this little extension here. 134 00:13:45,640 --> 00:13:51,460 Any double top now that we use from this point forward we'll have this functionality and it works the 135 00:13:51,460 --> 00:13:53,550 same way with it with protocols. 136 00:13:53,830 --> 00:14:02,320 So any extension that you add all of your types that conform to that protocol get that functionality 137 00:14:02,770 --> 00:14:04,720 just lock in this type extension. 138 00:14:04,870 --> 00:14:11,020 All doubles from now on to my program or my application will have the ability to call dollar string 139 00:14:11,080 --> 00:14:15,300 and print out a nicely formatted dollar amount. 140 00:14:15,400 --> 00:14:24,130 So I know this is a fairly short lesson here but I think it pretty well demonstrated the power of protocols 141 00:14:24,340 --> 00:14:31,010 protocol extensions and in the next lesson we're going to go for generics briefly kind of like this 142 00:14:31,630 --> 00:14:36,040 and then after that we'll get into some real world practical 143 00:14:39,680 --> 00:14:43,170 uses for protocols and protocols in a program. 144 00:14:43,170 --> 00:14:45,410 So until next time we'll see.