1 00:00:01,810 --> 00:00:02,940 A what's up everyone. 2 00:00:02,940 --> 00:00:04,970 Mark Price you're a dub slopes dot com. 3 00:00:04,980 --> 00:00:12,020 And today we're going to talk about inheritance not like the inheritance you got from your grandfather. 4 00:00:12,120 --> 00:00:16,590 You know when all your peers were out there working their butts off you know failing and failing and 5 00:00:16,590 --> 00:00:20,700 failing again and they're sweating and bleeding and you know you're out there and you get an inheritance 6 00:00:20,700 --> 00:00:22,890 and you're just like hey here's my Bugatti. 7 00:00:22,920 --> 00:00:23,770 You guys suck. 8 00:00:24,030 --> 00:00:25,620 Yes not one of those kind of things. 9 00:00:25,770 --> 00:00:26,510 It's a little bit different. 10 00:00:26,510 --> 00:00:34,290 It's more so like an inheritance of features more like I have red hair because my grandfather has red 11 00:00:34,290 --> 00:00:34,580 hair. 12 00:00:34,590 --> 00:00:38,450 You've been Herrod some type of features from some type of relative. 13 00:00:38,460 --> 00:00:47,330 So I'm going to get started with the playground and we're going to call this in heritance inheritance. 14 00:00:47,350 --> 00:00:49,900 It's one of those words that's easy to misspell. 15 00:00:50,100 --> 00:00:53,390 Inheritance is a principle of object oriented programming. 16 00:00:53,580 --> 00:00:54,050 OK. 17 00:00:54,060 --> 00:00:55,330 Object oriented programming. 18 00:00:55,330 --> 00:01:01,350 So a perfect example is continuing on with a car or a vehicle. 19 00:01:01,410 --> 00:01:07,590 We've got a view class OK and a vehicle class has some basic features less we'll will go ahead and say 20 00:01:07,590 --> 00:01:10,290 like var tires equals four. 21 00:01:10,350 --> 00:01:16,540 You've seen something like this before and then bar you know make of type string. 22 00:01:16,560 --> 00:01:20,390 But right now there's nothing in it bar model of type string. 23 00:01:20,640 --> 00:01:21,230 OK. 24 00:01:21,450 --> 00:01:33,870 And we said phunk drive and then we can say phunk for aik OK and save our current speed of type let's 25 00:01:33,870 --> 00:01:34,940 say double. 26 00:01:35,660 --> 00:01:36,890 And we started off at zero. 27 00:01:36,920 --> 00:01:38,170 The cars in moving. 28 00:01:38,310 --> 00:01:45,630 And so maybe OK let's say let's say you are creating can complex drive algorithm where it's going to 29 00:01:45,630 --> 00:01:47,330 move accelerate the car forward. 30 00:01:47,520 --> 00:01:54,900 So we pass in the speed increase K of type double. 31 00:01:55,150 --> 00:01:56,260 And then maybe the base. 32 00:01:56,410 --> 00:02:01,600 So for a basic car the basic algorithm is this it is this current speed. 33 00:02:02,490 --> 00:02:03,790 OK. 34 00:02:04,210 --> 00:02:10,430 Plus equals speed increase times. 35 00:02:10,540 --> 00:02:18,400 Let's say two let's say that was the algorithm some random arbitrary algorithm the current speed of 36 00:02:18,400 --> 00:02:23,690 the vehicle equals the current speed plus speed increase times 2. 37 00:02:24,180 --> 00:02:27,740 Now this going and create what's called a subclass. 38 00:02:27,740 --> 00:02:30,630 OK so this is a class let's create a subclass. 39 00:02:30,850 --> 00:02:32,610 We're going to show inheritance here. 40 00:02:32,620 --> 00:02:33,790 So a class 41 00:02:37,300 --> 00:02:38,220 what do I want to say. 42 00:02:38,230 --> 00:02:40,430 Class BMW. 43 00:02:41,920 --> 00:02:46,180 OK class BMW or even better. 44 00:02:46,180 --> 00:02:47,820 How about sports car. 45 00:02:47,830 --> 00:02:55,030 Just for fun sports car inherits from vehicles so you start inheritance by putting a colon here and 46 00:02:55,030 --> 00:03:01,570 then specifying the type K which is this this is the type the type or class that you want to inherit 47 00:03:01,570 --> 00:03:03,000 from. 48 00:03:03,010 --> 00:03:04,710 Now this is really cool there's nothing in here right. 49 00:03:04,720 --> 00:03:05,590 Nothing at all. 50 00:03:05,770 --> 00:03:11,620 But you can still access the properties of the parent class so on this sports car you know tires are 51 00:03:11,620 --> 00:03:15,790 going to stay the same but you know maybe we can set the make and model so I don't have to recreate 52 00:03:15,790 --> 00:03:25,490 those which is really cool I can say make equals and let's say BMW and model equals the say three series. 53 00:03:25,520 --> 00:03:26,050 OK. 54 00:03:26,380 --> 00:03:28,340 So we've got to make it a model. 55 00:03:31,470 --> 00:03:40,370 What we need to do here actually is create an initialiser first like so. 56 00:03:40,370 --> 00:03:40,640 All right. 57 00:03:40,640 --> 00:03:46,310 And then in here we can set our make and our model like so it's yelling at us because it wants us to 58 00:03:46,550 --> 00:03:47,490 override it. 59 00:03:52,370 --> 00:03:52,990 Yeah. 60 00:03:53,270 --> 00:04:00,810 So we need to call super and it super and it just some boilerplate stuff you've got to do in every class. 61 00:04:01,870 --> 00:04:02,360 OK. 62 00:04:02,510 --> 00:04:07,310 So every single class has by default an initialization function but you don't see or hear because we 63 00:04:07,310 --> 00:04:08,670 did not implement it. 64 00:04:08,840 --> 00:04:11,880 So let's implement it now on the parent class. 65 00:04:14,090 --> 00:04:14,650 OK. 66 00:04:14,940 --> 00:04:17,970 So we've got to initialize initialiser on the parent class. 67 00:04:18,000 --> 00:04:20,490 And initialiser here in the subclass. 68 00:04:20,670 --> 00:04:22,470 And this is interesting. 69 00:04:22,560 --> 00:04:25,020 We're calling super init on the parent class. 70 00:04:25,020 --> 00:04:25,750 What does that even mean. 71 00:04:25,770 --> 00:04:27,860 Well let's print this out. 72 00:04:27,870 --> 00:04:30,240 I am the parent. 73 00:04:30,720 --> 00:04:31,080 OK. 74 00:04:31,080 --> 00:04:33,210 And then just print this down here. 75 00:04:34,230 --> 00:04:42,240 I am the child and what I want to do is just create an instance of this class penning the code doesn't 76 00:04:42,240 --> 00:04:44,360 crash on us. 77 00:04:44,760 --> 00:04:46,260 It crashed. 78 00:04:46,260 --> 00:04:54,170 So OK what I want to do is create an instance of the sports car so let car equals a new sports car. 79 00:04:55,050 --> 00:05:01,880 And what's interesting in the if you decide to load I am the parent Prince and I am the child of what's 80 00:05:01,880 --> 00:05:02,870 happening here. 81 00:05:02,900 --> 00:05:08,120 So we create the sports car and then this initialiser is called and the override function says I want 82 00:05:08,120 --> 00:05:10,310 to override the parents initialiser function. 83 00:05:10,310 --> 00:05:12,210 So it won't be called at all. 84 00:05:12,590 --> 00:05:15,090 But then we actually call it here explicitly. 85 00:05:15,260 --> 00:05:19,260 So then that's going to go back up to the parent class and call was whatever in it. 86 00:05:19,280 --> 00:05:23,070 So sometimes parent classes have set up or things like that and introduce We want to call it. 87 00:05:23,120 --> 00:05:28,620 It's typical to call the parent class and then to create your own functionality which is really cool. 88 00:05:28,850 --> 00:05:31,360 OK so here's our sports car. 89 00:05:31,400 --> 00:05:31,760 Awesome. 90 00:05:31,760 --> 00:05:36,030 Now let's air our sports car needs to drive faster than the standard algorithm. 91 00:05:36,050 --> 00:05:41,130 So what we can do is we can even override the functions so I can type and drive. 92 00:05:41,180 --> 00:05:42,440 That's going to override it. 93 00:05:42,680 --> 00:05:48,560 And now what I could do instead of current speed being equal to this I can say current speed plus equals 94 00:05:48,650 --> 00:05:52,310 speed increase times three. 95 00:05:52,460 --> 00:05:55,320 So this one is times too but this was times three. 96 00:05:55,460 --> 00:06:00,660 And now the child's class we know that every car needs to have a drive function. 97 00:06:00,740 --> 00:06:01,630 And so that's great. 98 00:06:01,640 --> 00:06:05,360 Like why would we we wouldn't want to create a bunch of different classes and re-implement this function 99 00:06:05,390 --> 00:06:06,650 every single time. 100 00:06:06,680 --> 00:06:10,580 So it's already pre-built and we just wrote it once and we overwrote it here which is great. 101 00:06:10,610 --> 00:06:16,600 Every vehicle needs to be able to drive but its implementation could be different purview. 102 00:06:16,640 --> 00:06:21,620 Is a Ford F-150 going to accelerate differently than a Ford Mustang. 103 00:06:21,710 --> 00:06:24,220 Yes every car is going to have its acceleration. 104 00:06:24,380 --> 00:06:28,620 Therefore it would have its own code here in the functions that it's overriding. 105 00:06:28,640 --> 00:06:31,530 And of course you can override the properties as well too. 106 00:06:31,850 --> 00:06:36,470 So the whole point of this lesson we could go way down this rabbit hole where we're not going to. 107 00:06:36,590 --> 00:06:42,560 The whole point of this lesson to know is that you can create a parent class and children classes can 108 00:06:42,560 --> 00:06:45,640 inherit from that parent class and you can do more than one. 109 00:06:45,650 --> 00:06:50,960 So if we bought a sports car we could say class truck inherits from view school we could have done the 110 00:06:50,960 --> 00:06:52,360 exact same thing there. 111 00:06:52,550 --> 00:07:00,250 And then you know initialiser or let's let's just copy what we've got here is make it really easy so 112 00:07:00,250 --> 00:07:01,770 it doesn't yell at us OK. 113 00:07:02,020 --> 00:07:03,700 And you know we can get rid of these here. 114 00:07:04,210 --> 00:07:11,560 OK and then a trunk a truck could have its own drive function that you know speed increase you know 115 00:07:12,040 --> 00:07:18,340 plus equals or excuse me current speed plus equal speed increase. 116 00:07:18,340 --> 00:07:20,980 You know without multiplying it by a multiplier. 117 00:07:21,220 --> 00:07:25,870 And so anyway now we've got two different classes here that both inherit from Buca they both have a 118 00:07:25,870 --> 00:07:31,810 drive function but their implementation is different and why this is important is because it helps you 119 00:07:32,680 --> 00:07:36,850 create objects that can adapt to different situations. 120 00:07:36,850 --> 00:07:43,690 For instance you know on Instagram you may have a parent class that has you know a specific base filter 121 00:07:43,720 --> 00:07:47,620 but then you may have different filters like Valencia and other things that have their own algorithms 122 00:07:48,040 --> 00:07:49,410 that they need to implement. 123 00:07:49,420 --> 00:07:54,280 So rather than putting it all one giant class file they could easily have created a parent class which 124 00:07:54,280 --> 00:07:58,240 creates a deep filter and then they can override it and add some other functionality to it for those 125 00:07:58,240 --> 00:07:59,940 specific filters. 126 00:07:59,980 --> 00:08:04,930 Again all kinds of things you can do with classes objects and inheritance but that's all you need to 127 00:08:04,970 --> 00:08:09,220 know now you're going to learn about it more as you use it in Iowa development. 128 00:08:09,220 --> 00:08:14,570 So Mark Price your DENSELOW dot com move movin on an ad for.