1 00:00:01,040 --> 00:00:10,610 OK, so we are continuing on with our polymorphic project, but we are going to transition into something 2 00:00:10,610 --> 00:00:17,360 that isn't necessarily tied to polymorphism, it's kind of a stand alone topic, but it will be one 3 00:00:17,360 --> 00:00:22,580 of our last topics we're talking about here in the programming half of this course. 4 00:00:23,780 --> 00:00:31,670 So before I tell you what this topic is, I just kind of want to talk about a potential function that 5 00:00:31,670 --> 00:00:37,430 we might want to add to this class, so this is not some super portant function. 6 00:00:37,910 --> 00:00:46,460 But let's say that in each one of the derive classes we wanted, a function called is bigger to see 7 00:00:46,460 --> 00:00:51,610 if one shape was bigger than the shape of the current shape of this class. 8 00:00:51,620 --> 00:00:59,180 So let's say I just have something like a Boolean function, and I want to say like, call it, let's 9 00:00:59,180 --> 00:01:03,230 say, is a bigger shape. 10 00:01:04,520 --> 00:01:13,340 And what we want to know is, is that this object, which is the object that's being called upon, is 11 00:01:13,340 --> 00:01:17,540 it area bigger than a specific shape that we would pass to this? 12 00:01:17,960 --> 00:01:20,540 And what if we don't want to limit it to triangles? 13 00:01:20,540 --> 00:01:24,290 What if we want it to be a triangle or a circle or a rectangle? 14 00:01:25,800 --> 00:01:34,380 So the thing about that is it creates kind of a problem, right, because like, let's say we want to 15 00:01:34,380 --> 00:01:39,390 have this in each one of the classes, not that really even matters, but I don't know what type to 16 00:01:39,390 --> 00:01:40,110 put here. 17 00:01:40,710 --> 00:01:45,300 If I wanted to compare a circle, you know, I want something to like, inherit. 18 00:01:45,900 --> 00:01:50,850 We're not in here to want something to include the circle class, so I can have access to it to know 19 00:01:50,850 --> 00:01:51,480 this type. 20 00:01:52,770 --> 00:01:58,270 But like, not even considering that, what if I don't want to limit it to a circle? 21 00:01:58,270 --> 00:02:06,900 What if I want it to be maybe another triangle or I want it to be a rectangle or something like that? 22 00:02:06,910 --> 00:02:10,530 So, you know, that's kind of that's kind of a problem. 23 00:02:11,950 --> 00:02:16,240 That I that I can't do any of those, I won't know which one it is. 24 00:02:16,360 --> 00:02:18,070 So how would we resolve that? 25 00:02:18,550 --> 00:02:24,040 And this is where the new Typekit comes in and this is something called a template. 26 00:02:25,090 --> 00:02:34,780 So what we can do is we can kind of define and be ambiguous type and use that ambiguous type as the 27 00:02:34,780 --> 00:02:38,950 data type here inside of our parameters. 28 00:02:39,370 --> 00:02:43,180 That way, it won't really be set to a specific data type. 29 00:02:43,210 --> 00:02:48,820 It'll kind of just be resolved at the time in which something is passed to this function. 30 00:02:49,990 --> 00:02:52,150 So how would we do something like that? 31 00:02:52,180 --> 00:03:00,100 Well, I'm just going to implement it just in triangle, and then I'm going to challenge you to implement 32 00:03:00,100 --> 00:03:06,730 it across all of the classes by also adding it as an abstract method to the base class. 33 00:03:07,330 --> 00:03:11,530 And then I'll go ahead and do that so you can see how that would work. 34 00:03:12,220 --> 00:03:19,630 But first off, I'm just going to show you how a function template can work here just by using the triangle 35 00:03:19,630 --> 00:03:21,640 class as an example. 36 00:03:22,750 --> 00:03:27,240 So what I'm going to do is I'm going to type the word template universe and see line. 37 00:03:27,250 --> 00:03:34,330 It's nice because it brings up not only the word template for me, but it also shows the next syntax 38 00:03:34,330 --> 00:03:35,040 right here. 39 00:03:35,050 --> 00:03:40,680 It needs to go inside of angle brackets similar to like when you used a vector. 40 00:03:40,690 --> 00:03:46,990 So if you had a vector and you said vector of type and we're going to do something similar where we 41 00:03:46,990 --> 00:03:54,130 say template and then we're just going to put some type of like class name in here, ambiguous class 42 00:03:54,130 --> 00:03:54,520 name. 43 00:03:55,300 --> 00:03:58,810 So I press tab and it already gives me those little angle brackets. 44 00:03:59,410 --> 00:04:06,220 So what I'm going to say is inside of here, I'm just going to say Class T, and this is going to represent 45 00:04:06,220 --> 00:04:09,430 our ambiguous templated data type here. 46 00:04:10,590 --> 00:04:18,810 So I have to put this above the member function that I'm interested in having be a template, no function, 47 00:04:18,810 --> 00:04:19,170 so. 48 00:04:20,290 --> 00:04:30,480 And here I'm going to use the capital T as the data type now, and I'm just going to say T shape. 49 00:04:30,990 --> 00:04:37,830 So the type of the shape is kind of this ambiguous template, ambiguous template, and we're going to 50 00:04:37,830 --> 00:04:41,430 call that type T because we have this class T in here. 51 00:04:43,170 --> 00:04:52,860 So once I put that I actually need to have in C++ the definition of the function and the implementation 52 00:04:52,860 --> 00:04:54,930 of the function in the same file. 53 00:04:54,930 --> 00:05:00,420 So I can't just prototype the template and throw it into another file like this, I have to actually 54 00:05:00,420 --> 00:05:00,810 put it. 55 00:05:02,130 --> 00:05:07,290 In here in this header, since we're just using the header, it would be like that anyways, right? 56 00:05:07,290 --> 00:05:10,380 We have our implementations here, so no big deal. 57 00:05:11,340 --> 00:05:21,150 So I'm going to go ahead and just check to see whether the area of the this object is bigger or less 58 00:05:21,150 --> 00:05:28,320 than the area of the T shape past object to the method. 59 00:05:29,220 --> 00:05:31,260 So just one liner here, really. 60 00:05:31,260 --> 00:05:39,330 I'm just going to say return and I'm going to say this, which is the object that's being called upon, 61 00:05:39,330 --> 00:05:39,600 right? 62 00:05:39,870 --> 00:05:41,010 So it'll be our triangle. 63 00:05:41,460 --> 00:05:43,710 I will say if this arrow. 64 00:05:45,470 --> 00:05:54,100 Area is greater than or I'm just going to say return, sorry. 65 00:05:54,380 --> 00:06:00,230 What we want to do is we want to see if this shape in here has a greater area than this object. 66 00:06:00,240 --> 00:06:11,150 So I'm just going to say return this area less than shape and shape. 67 00:06:11,570 --> 00:06:12,230 I could have. 68 00:06:12,230 --> 00:06:17,300 This is what I'm going to do is just reference the pointer, so I'll just do a dot. 69 00:06:17,930 --> 00:06:23,270 So I'm going to say shape dot area. 70 00:06:25,610 --> 00:06:29,060 And then so what I'll do is when I'm in the client file. 71 00:06:29,420 --> 00:06:37,520 Since I have pointers here, I am going to just reference the pointer so I could pass an actual object 72 00:06:38,000 --> 00:06:45,290 into here, like a sharp object, like some ambiguous one, some, you know, type of shape object, 73 00:06:45,290 --> 00:06:48,830 whether it be a triangle circle or rectangle, but it's not going to be a pointer. 74 00:06:49,130 --> 00:06:51,830 So that's why I'm going to expect just a shape. 75 00:06:51,830 --> 00:06:53,000 That's why I'm using the dot here. 76 00:06:54,620 --> 00:06:58,860 So now I have this template here and so I can use this T. 77 00:07:00,580 --> 00:07:06,220 And we can automatically resolve what type of shape is going to get passed here and see, since they 78 00:07:06,220 --> 00:07:12,720 all have an area, we know that we can just use this line and call area on both this and the shaped 79 00:07:12,860 --> 00:07:13,210 area. 80 00:07:15,580 --> 00:07:19,270 So let's go ahead and test this out, right? 81 00:07:19,480 --> 00:07:25,990 So I'm going to go ahead and go to my main and then what I'm going to do is I'm just going to put some 82 00:07:25,990 --> 00:07:26,590 sort of. 83 00:07:30,050 --> 00:07:35,030 If check here and let's see what happens when I try and use this. 84 00:07:35,210 --> 00:07:38,330 So let's say we put it in triangle, right? 85 00:07:38,340 --> 00:07:41,630 So let's go ahead and see if we can use it in triangle. 86 00:07:42,560 --> 00:07:45,040 So if I go t ts a point, right? 87 00:07:45,050 --> 00:07:46,190 And I go arrow. 88 00:07:47,450 --> 00:07:52,240 Notice that it's not giving me the that function from triangle. 89 00:07:52,250 --> 00:07:55,540 So these functions were fine, right? 90 00:07:55,610 --> 00:08:05,960 You notice that these two functions here were ones that were virtual functions in the abstract base 91 00:08:05,960 --> 00:08:10,120 class for all of the shapes in all of the drive class shapes. 92 00:08:10,120 --> 00:08:11,440 So they all have to have these. 93 00:08:11,450 --> 00:08:16,500 So it's because I'm actually declaring the pointer as shape Typekit. 94 00:08:16,500 --> 00:08:18,370 It's not really letting me access that. 95 00:08:18,380 --> 00:08:23,240 So if I try and force this, let's see what's it called is bigger shape. 96 00:08:23,780 --> 00:08:30,320 If I try and say Arrow is bigger shape, it doesn't like that doesn't recognize that function. 97 00:08:30,320 --> 00:08:35,960 So sometimes we can do to resolve this is I'm actually just going to change all of these to order. 98 00:08:45,590 --> 00:08:47,630 So now if I go. 99 00:08:49,190 --> 00:08:50,280 And I do this arrow. 100 00:08:50,300 --> 00:08:56,900 You notice I now have access to the is bigger shape memory function, so I can say if. 101 00:08:58,400 --> 00:09:00,780 Is bigger shape and then let me pass a shape, right? 102 00:09:00,800 --> 00:09:06,560 So how about we pass on little reference like this rectangle? 103 00:09:06,560 --> 00:09:09,630 So I'll say star to reference it, right? 104 00:09:09,680 --> 00:09:10,610 A star? 105 00:09:12,560 --> 00:09:16,610 How do you reference it and give me not the pointer, but the actual rectangle object? 106 00:09:17,150 --> 00:09:22,580 And so if what I'm checking right here is, I'm saying like, Oh, let's check it to see, is it true 107 00:09:22,580 --> 00:09:27,290 or false, whether the rectangles area is bigger than the triangles area, right? 108 00:09:28,830 --> 00:09:39,990 So in this case, I'll just print something out and I'll say on the rectangle is bigger. 109 00:09:41,130 --> 00:09:43,890 I can even do something like this like, look, I could put the tape. 110 00:09:44,010 --> 00:09:48,870 So I'll just say our tape 111 00:09:55,290 --> 00:09:58,260 is bigger than. 112 00:10:01,440 --> 00:10:04,590 Uh, I guess I should put the right. 113 00:10:05,920 --> 00:10:08,290 Well, they say the 114 00:10:11,380 --> 00:10:18,460 are Typekit is bigger than me, and I'll just say T type. 115 00:10:24,670 --> 00:10:24,960 Cool. 116 00:10:25,520 --> 00:10:32,450 So if the rectangle is in fact bigger than the triangle, then that should print out, OK? 117 00:10:33,840 --> 00:10:38,850 So I didn't put any go. 118 00:10:40,220 --> 00:10:45,330 So you notice right here, look at our rectangle, so it has a width of one and a height of one. 119 00:10:45,440 --> 00:10:52,490 And look at a triangle here, let's just say if we change this to like. 120 00:10:54,670 --> 00:10:55,150 Or. 121 00:10:56,200 --> 00:10:58,480 And seven something like that. 122 00:10:59,830 --> 00:11:03,790 You know, this would be twenty eight divided by two. 123 00:11:05,630 --> 00:11:11,660 So there would be 14 step and mean bigger than the rectangle, right, so we can even double check that 124 00:11:11,660 --> 00:11:12,000 here. 125 00:11:12,020 --> 00:11:17,450 So why don't we just print out and uh, let's just say. 126 00:11:19,820 --> 00:11:21,320 The are type one. 127 00:11:21,320 --> 00:11:22,370 Why don't we do this 128 00:11:25,670 --> 00:11:32,750 with area and we'll do our area? 129 00:11:34,750 --> 00:11:36,430 It's bigger than a T tie 130 00:11:40,480 --> 00:11:42,670 with area. 131 00:11:46,300 --> 00:11:55,420 And the key area is kind of a long running line there. 132 00:11:57,670 --> 00:12:04,210 But let's go ahead and that out, so I can only do this like decimals, we can make changes to you 133 00:12:07,030 --> 00:12:10,060 like anything as well, so let's go ahead and just run this. 134 00:12:12,560 --> 00:12:14,370 So it looks like it's not bigger. 135 00:12:14,390 --> 00:12:19,370 So what if I change this to like 10 and I changed this to like 11? 136 00:12:23,250 --> 00:12:27,070 Cool, so you notice that I put that with and without that there. 137 00:12:27,090 --> 00:12:30,060 So let's go ahead and read that again about the space. 138 00:12:30,630 --> 00:12:36,360 So the rectangle with area one sixteen point six is bigger than the triangle with area fifteen point 139 00:12:36,720 --> 00:12:38,130 seven five. 140 00:12:38,520 --> 00:12:40,300 So I should put a space there to. 141 00:12:43,850 --> 00:12:46,070 So pretty cool, right? 142 00:12:46,430 --> 00:12:50,780 So it's able to actually resolve this for anything like what if we change it to something else? 143 00:12:50,780 --> 00:12:52,940 So I do the see for the circle. 144 00:12:53,270 --> 00:12:55,970 And now we're passing the circle instead. 145 00:12:56,360 --> 00:12:58,190 So let's go ahead and do that. 146 00:13:00,960 --> 00:13:02,880 See notice now, it says. 147 00:13:05,040 --> 00:13:06,120 We'd want to put the. 148 00:13:07,180 --> 00:13:09,420 Different type for that, we'd want to put this circle right? 149 00:13:09,570 --> 00:13:11,970 So the chances to see. 150 00:13:14,350 --> 00:13:15,760 Because I change that to see. 151 00:13:17,460 --> 00:13:24,000 So let's see what it says here, so says the circle with area to seventy seven point eighty seven speaking 152 00:13:24,000 --> 00:13:27,030 in the triangle area fifteen point seven five. 153 00:13:30,820 --> 00:13:32,140 So pretty cool, right? 154 00:13:33,190 --> 00:13:36,640 So it's checking that that's better or bigger. 155 00:13:36,940 --> 00:13:43,990 So what I want to challenge you to do now is to be able to kind of incorporate this with our polymorphic 156 00:13:43,990 --> 00:13:44,530 design. 157 00:13:44,540 --> 00:13:51,190 So you should be able to go into shape and make this present in each one of the. 158 00:13:54,320 --> 00:13:55,460 Drive classes here. 159 00:13:56,520 --> 00:14:04,620 So you have some sort of is bigger shape, so see if you can actually make that happen. 160 00:14:05,550 --> 00:14:08,490 You may not be able to make it an abstract base class. 161 00:14:09,450 --> 00:14:11,310 Sorry, an abstract function. 162 00:14:11,480 --> 00:14:12,870 You know, that's pure ritual. 163 00:14:13,270 --> 00:14:16,860 But just go ahead and try and see if you can make it work. 164 00:14:17,760 --> 00:14:18,110 All right. 165 00:14:18,150 --> 00:14:23,460 So with that, I will see you in the next video in which I will go over that solution with you. 166 00:14:23,850 --> 00:14:31,650 And then we will talk about not only using templates for templated memory functions or just functions 167 00:14:31,650 --> 00:14:32,310 in general. 168 00:14:33,330 --> 00:14:35,790 We'll also be talking about using templates for classes.