1 00:00:08,150 --> 00:00:11,110 Everybody what's going on this is Caleb with devah slopes dot com. 2 00:00:11,130 --> 00:00:15,540 And in this video we're going to start talking about protocols and delegates. 3 00:00:15,540 --> 00:00:15,990 OK. 4 00:00:16,290 --> 00:00:24,090 Protocols are really really amazing feature of swift particularly but of couple other programming languages. 5 00:00:24,090 --> 00:00:26,410 And basically what a protocol is is. 6 00:00:26,430 --> 00:00:27,890 Think of it like a blueprint. 7 00:00:28,020 --> 00:00:28,480 OK. 8 00:00:28,740 --> 00:00:35,940 Now this blueprint can contain methods or functions properties and other requirements that fit a particular 9 00:00:35,940 --> 00:00:38,950 task or like a piece of functionality. 10 00:00:39,000 --> 00:00:47,010 And what we're able to do is we're able to conform to a certain protocol from a class form from a structure 11 00:00:47,280 --> 00:00:50,780 or even an enumeration which you'll see later in this video. 12 00:00:51,120 --> 00:00:58,320 And that enumeration or that structure or that class can provide the actual implementation of the methods 13 00:00:58,320 --> 00:01:00,840 or properties or whatever you set in your protocol. 14 00:01:00,840 --> 00:01:02,410 So really really cool. 15 00:01:02,430 --> 00:01:04,100 Let's dive into it now. 16 00:01:04,290 --> 00:01:08,840 You're going to want to open up X code beta and we're going to get started with a playground. 17 00:01:08,960 --> 00:01:11,020 We pull it open in the right window. 18 00:01:11,030 --> 00:01:20,290 Here we go and just click blank and I'm going to actually let's put this in the proper folder for protocols. 19 00:01:20,370 --> 00:01:24,960 Call this protocol mania. 20 00:01:24,960 --> 00:01:26,240 That sounds fun. 21 00:01:26,370 --> 00:01:27,430 Press create. 22 00:01:27,840 --> 00:01:28,910 And here we go. 23 00:01:29,150 --> 00:01:33,530 OK let me bump up the font size a bit and let's get rid of this. 24 00:01:33,540 --> 00:01:35,130 We do need you like it. 25 00:01:35,280 --> 00:01:37,140 We don't need that string. 26 00:01:37,140 --> 00:01:37,880 And great. 27 00:01:37,950 --> 00:01:39,570 OK let's let's get after it. 28 00:01:39,570 --> 00:01:46,860 So let me start by showing you the protocol syntax which you can use by simply typing protocol and then 29 00:01:46,860 --> 00:01:49,350 giving a name to your protocol. 30 00:01:49,380 --> 00:01:55,060 Now it's the same thing that you would do for naming a class or an enumeration or a structure. 31 00:01:55,350 --> 00:02:01,230 All capital first letters of all of the words so if there's three words there's three capital letters 32 00:02:02,040 --> 00:02:04,890 for this one we're just going to call it number and k. 33 00:02:04,950 --> 00:02:09,390 And we're going to be doing some fun things with different types of numbers and I'm just going to show 34 00:02:09,390 --> 00:02:12,330 you how protocols can be valuable. 35 00:02:12,480 --> 00:02:18,000 Then we're going to do another example using some classes and a couple of other things to show you how 36 00:02:18,000 --> 00:02:23,970 it can be used in class instances and then in the next couple of videos we're going to use protocols 37 00:02:24,000 --> 00:02:27,930 as a means of delegating information between View controllers and lots of really cool stuff. 38 00:02:27,930 --> 00:02:32,320 So let's just begin by getting familiar with protocols in general. 39 00:02:32,370 --> 00:02:38,830 So inside of a protocol you can include methods and you can also include properties. 40 00:02:38,850 --> 00:02:44,140 So I'm going to include a property in this protocol called a float value and I'm going to declare it 41 00:02:44,150 --> 00:02:48,300 by typing var float value of type float. 42 00:02:48,600 --> 00:02:55,110 And if we want this property to be accessible we can go ahead and give it some curly braces and then 43 00:02:55,110 --> 00:03:01,730 inside these curly braces we can choose to put get or get set. 44 00:03:01,980 --> 00:03:09,470 And that will allow us to either just get the value of the flow value or be able to set it as well. 45 00:03:09,510 --> 00:03:14,540 But for this video we're only going to need to get the value and I'll show you why later. 46 00:03:14,550 --> 00:03:20,550 Now let's say that we wanted to include a function as well maybe get flow value ok. 47 00:03:20,880 --> 00:03:29,010 You just declare it like this func get float value and you include the parentheses for showing that 48 00:03:29,010 --> 00:03:34,650 it's a function but you're not going to put the curly braces and watch what happens when I do that protocol 49 00:03:34,650 --> 00:03:36,000 methods may not have bodies. 50 00:03:36,000 --> 00:03:42,530 Remember the description I said at the beginning of the video the protocol is not where you declare 51 00:03:42,540 --> 00:03:43,850 the implementation. 52 00:03:43,950 --> 00:03:49,650 OK wherever you conform to this protocol later on that's where you'll declare the implementation and 53 00:03:49,650 --> 00:03:51,530 I'll show you what I mean. 54 00:03:51,570 --> 00:03:56,960 But for now just get rid of this function and leave the variable float value. 55 00:03:56,970 --> 00:04:03,720 So what we can do with this protocol now is we can conform to it just like you would with subclassing. 56 00:04:03,720 --> 00:04:10,410 So if I wanted to create a square class and then create maybe a rectangle subclass that inherited from 57 00:04:10,410 --> 00:04:18,890 square I could do that by typing class square whip's where and then. 58 00:04:18,960 --> 00:04:23,640 Sorry I meant class Rectangle and I could inherit from class Square. 59 00:04:23,670 --> 00:04:25,120 That's one way I could do it. 60 00:04:25,320 --> 00:04:27,880 So for protocol's it's kind of the same thing. 61 00:04:28,170 --> 00:04:31,660 I'm going to make an extension of float. 62 00:04:31,770 --> 00:04:32,070 OK. 63 00:04:32,070 --> 00:04:37,070 Now if you've already seen the extension video that's great so you'll have some familiarity with extensions. 64 00:04:37,110 --> 00:04:44,120 I'm going to extend the float type and I'm going to conform to my protocol number. 65 00:04:44,130 --> 00:04:51,840 Now you'll notice there's going to be an issue that says type float does not conform to protocol number. 66 00:04:51,840 --> 00:04:54,980 Now remember I said that a protocol is sort of like a blueprint. 67 00:04:55,040 --> 00:04:55,230 Right. 68 00:04:55,230 --> 00:04:59,480 A set of instructions in order to set something up the right way. 69 00:04:59,490 --> 00:05:07,260 So what we're saying is if we conform to the protocol number we need to include the variable float value 70 00:05:07,920 --> 00:05:14,760 what we can do to do that is we can basically call float value and you'll notice that it shows up right 71 00:05:14,760 --> 00:05:19,410 there and my list of properties if I press Enter you'll see that it passes it in. 72 00:05:19,590 --> 00:05:25,530 But what we need to do is we need to return a certain value to this variable so we can do that by typing 73 00:05:25,530 --> 00:05:26,430 return. 74 00:05:26,730 --> 00:05:31,140 And let's think about what do we need to return an extension of float. 75 00:05:31,230 --> 00:05:34,370 We need to return whatever value is passed in as a float. 76 00:05:34,380 --> 00:05:40,150 So let's say I create a variable of type float and I should return self to float value. 77 00:05:40,200 --> 00:05:43,230 Right because it already is of type float. 78 00:05:43,230 --> 00:05:50,850 So that's great and all but that basically is going to give us the ability to pull out the float value 79 00:05:50,850 --> 00:05:52,680 of a certain constant or variable. 80 00:05:52,680 --> 00:05:59,840 So like for instance I could do this let 4 of type float equals four. 81 00:05:59,880 --> 00:06:04,080 And now if I wanted to get the explicit float value I could type for. 82 00:06:04,290 --> 00:06:11,310 And as you can see we can pull out the float value in case we've extended float to include the property 83 00:06:11,310 --> 00:06:12,330 float value. 84 00:06:12,330 --> 00:06:13,270 Pretty cool. 85 00:06:13,590 --> 00:06:24,120 So now let's think if I wanted to do some math maybe between of our three of type int equals 3 and var 86 00:06:24,150 --> 00:06:30,570 4 of type float equals 4 if I wanted to do three plus four. 87 00:06:30,870 --> 00:06:32,380 I'm going to get an error. 88 00:06:32,460 --> 00:06:38,760 And the reason for that is because the types are not compatible int and float are not the same so we 89 00:06:38,760 --> 00:06:41,360 can't add them because it doesn't know how to do that. 90 00:06:41,400 --> 00:06:48,600 But what we can do is we can write an extension of all of our number types and we can give it the float 91 00:06:48,600 --> 00:06:52,830 value property that's going to essentially convert it into a float. 92 00:06:52,830 --> 00:06:53,910 Let's do that. 93 00:06:53,910 --> 00:07:00,690 So let's go ahead and type extension and let's extend double because that's one of our number types. 94 00:07:00,690 --> 00:07:07,050 So we're going to conform to the protocol number and then to officially conform we need to include all 95 00:07:07,050 --> 00:07:07,800 the properties. 96 00:07:07,800 --> 00:07:12,030 So let's go ahead and give it the value for float value. 97 00:07:12,360 --> 00:07:16,260 And now we need to think what are we going to return this time. 98 00:07:16,500 --> 00:07:21,900 We need to return but we need to think if a double is coming in. 99 00:07:21,960 --> 00:07:28,350 We need to somehow convert that into a float and how we can do that is by doing typecasting. 100 00:07:28,380 --> 00:07:35,820 So go ahead and type float and we're going to give it self meaning whatever double value we have. 101 00:07:35,970 --> 00:07:44,050 We can pass that in itself and we can encapsulate it as a float and return that to to our variable. 102 00:07:44,250 --> 00:07:48,750 So instead of doing three let's let's change that to a double. 103 00:07:48,810 --> 00:07:51,630 It's still not going to work because they're not related types. 104 00:07:51,690 --> 00:07:59,730 But what I can do now is I can type three float value and I can add that to for now type compatible. 105 00:07:59,730 --> 00:08:06,360 So if I actually were to do this it would print out three plus four equals seven successfully and it 106 00:08:06,360 --> 00:08:12,480 would be of type float because using my extension I can now pull out the specific float value for that 107 00:08:12,480 --> 00:08:13,110 variables. 108 00:08:13,110 --> 00:08:14,760 Pretty awesome. 109 00:08:14,760 --> 00:08:22,290 Let's go ahead and let's get rid of that and let's keep extending this extension of not of type number 110 00:08:22,290 --> 00:08:24,970 but we're conforming to the number protocol. 111 00:08:25,260 --> 00:08:29,360 Let's go ahead and call float value and let's return just like before. 112 00:08:29,360 --> 00:08:32,270 Float. 113 00:08:32,340 --> 00:08:36,200 We're going to encapsulate self and cast it as a float. 114 00:08:36,210 --> 00:08:42,300 Next we're going to go ahead and call extension you and because there are many times where we will have 115 00:08:42,420 --> 00:08:53,120 you int values go ahead and conform to the number protocol call float value and return float self. 116 00:08:53,370 --> 00:08:55,600 Self encapsulated as a float. 117 00:08:55,620 --> 00:09:00,180 So now we have four extensions we can access the float value of any of these. 118 00:09:00,180 --> 00:09:02,120 Now which is really cool. 119 00:09:02,190 --> 00:09:07,650 And now let's do our best to write an equation that's going to let us basically add numbers of unrelated 120 00:09:07,650 --> 00:09:08,230 types. 121 00:09:08,280 --> 00:09:14,820 So let's go ahead and let's create a variable called X and let's make it of type double and let's make 122 00:09:14,820 --> 00:09:18,220 sure that it's a double by adding some decimals at the end. 123 00:09:18,450 --> 00:09:26,910 Let's create another value called Y of type int and let's go ahead make that equal to 5 because it's 124 00:09:26,910 --> 00:09:29,200 an integer it must be whole value. 125 00:09:29,400 --> 00:09:32,090 And let's go ahead and let. 126 00:09:32,110 --> 00:09:33,930 Q I'm going to divide these. 127 00:09:33,930 --> 00:09:40,230 Let Q be the quotient and it's going to be equal to x divided by Y. 128 00:09:40,230 --> 00:09:42,590 OK let's see what happens. 129 00:09:42,660 --> 00:09:44,040 It looks like we're getting an error here. 130 00:09:44,040 --> 00:09:44,730 Check it out. 131 00:09:44,910 --> 00:09:45,840 It's saying 132 00:09:48,840 --> 00:09:56,280 the binary operator divide cannot be applied to operands of type double and int k so we're getting the 133 00:09:56,280 --> 00:09:58,370 same problem as before. 134 00:09:58,470 --> 00:10:02,670 But what we're going to do is we're going to write some functions here that will allow us to make these 135 00:10:02,670 --> 00:10:03,630 work nicely. 136 00:10:03,630 --> 00:10:09,900 Now one thing we could do is we could do X float value divided by wide float value. 137 00:10:09,910 --> 00:10:12,960 But what if we don't think to pull that out all the time. 138 00:10:13,150 --> 00:10:14,150 That might not work. 139 00:10:14,230 --> 00:10:17,230 So as you can see it does work to do this. 140 00:10:17,380 --> 00:10:21,410 But what if we just wanted to be able to divide unrelated types. 141 00:10:21,670 --> 00:10:27,480 We can write some functions that are going to allow us to override how these binary operators work. 142 00:10:27,490 --> 00:10:29,410 Let's do that really quick it's pretty cool. 143 00:10:29,650 --> 00:10:37,480 So go ahead and we're going to basically just write phunk add K and inside of add we're going to pass 144 00:10:37,480 --> 00:10:48,190 in two values right value a of type number k and value B of type number and we're using our protocol 145 00:10:48,190 --> 00:10:50,830 there is kind of like a class to pass in. 146 00:10:50,830 --> 00:10:57,940 Now inside this function if we're adding we're going to take value a whatever we pass in float value 147 00:10:58,660 --> 00:11:03,420 and we're gonna go ahead and add it to value be float value. 148 00:11:04,270 --> 00:11:09,670 The only issue is that we actually need to return a value here K and we're going to return a value of 149 00:11:09,670 --> 00:11:10,650 type float. 150 00:11:10,810 --> 00:11:17,590 Let's say we're just working with floats so we can return it like so return value a plus float value 151 00:11:18,010 --> 00:11:21,270 plus value B plus foot dot float value. 152 00:11:21,640 --> 00:11:23,190 So many so many floats there. 153 00:11:23,190 --> 00:11:23,600 OK. 154 00:11:23,770 --> 00:11:27,820 So that is how we can do the addition function. 155 00:11:28,000 --> 00:11:32,780 But what we're going to do is we're going to do this for addition subtraction division and multiplication. 156 00:11:32,780 --> 00:11:36,770 So copy this function just for time we're going to paste it a few times. 157 00:11:37,000 --> 00:11:42,910 I wouldn't normally do this but just for time time's sake we're going to replace plus with minus and 158 00:11:43,000 --> 00:11:50,410 do that again replace plus here with Divide and replace it there as well and then replace this with 159 00:11:50,410 --> 00:11:54,050 an asterisk for multiplication and do the same thing there. 160 00:11:54,050 --> 00:11:59,740 Now we have these functions whenever we call Plus it's going to use it like a function. 161 00:11:59,740 --> 00:12:01,400 We're going to take value a. 162 00:12:01,560 --> 00:12:04,410 Pass it in value B pass it in. 163 00:12:04,420 --> 00:12:06,370 Add them together and return the value. 164 00:12:06,370 --> 00:12:08,320 So now watch what happens. 165 00:12:08,320 --> 00:12:12,060 I have two unrelated types double and end. 166 00:12:12,460 --> 00:12:18,670 But when I use the division operand check out what happens it passes in these two values and it returns 167 00:12:18,670 --> 00:12:19,710 a float. 168 00:12:19,780 --> 00:12:20,490 It works. 169 00:12:20,500 --> 00:12:27,130 I am able to do operations on two unrelated types thanks to protocol's super super cool. 170 00:12:27,130 --> 00:12:34,330 So as you can see protocols are pretty awesome they allow us to basically set a blueprint for values 171 00:12:34,330 --> 00:12:37,010 that we are going to use or we'll need to use. 172 00:12:37,150 --> 00:12:40,090 And this is just one way they can be used. 173 00:12:40,150 --> 00:12:42,840 I think I'm actually going to split this video into two. 174 00:12:42,910 --> 00:12:48,490 And in the next video we're going to actually see how protocols can benefit us when using classes or 175 00:12:48,490 --> 00:12:50,530 structures et cetera et cetera. 176 00:12:50,530 --> 00:12:55,050 So let's go ahead and let's move over to the next video and I'll show you how to do that right now.