1 00:00:00,490 --> 00:00:03,010 ‫So now we're going to talk about classes. 2 00:00:03,010 --> 00:00:09,640 ‫And this is something that we are going to use a lot in this course, especially in the data structures 3 00:00:09,640 --> 00:00:10,420 ‫section. 4 00:00:10,990 --> 00:00:15,760 ‫My favorite analogy for a class is that it's like a cookie cutter. 5 00:00:15,760 --> 00:00:22,690 ‫It's something that you use to make cookies with or whatever object you're creating. 6 00:00:23,080 --> 00:00:29,710 ‫So for my example, the class that I'm going to create is actually going to be called Cookie. 7 00:00:30,350 --> 00:00:36,470 ‫So standard naming convention for a class as you always capitalize it, and then it will end with a 8 00:00:36,470 --> 00:00:44,030 ‫curly brace and then you put a semicolon after it and then classes will have attributes. 9 00:00:44,480 --> 00:00:51,680 ‫In this case, we'll have the attribute color, and typically you want to set your attributes to be 10 00:00:51,680 --> 00:00:52,580 ‫private. 11 00:00:52,820 --> 00:00:57,680 ‫And then also typically you'll have what is called a constructor. 12 00:00:57,950 --> 00:01:05,780 ‫A constructor is a member function that has the same name as the class, and most of your member functions 13 00:01:05,780 --> 00:01:08,060 ‫are going to be set to public. 14 00:01:08,640 --> 00:01:13,500 ‫So in this case, we're going to pass the constructor a string that is called color. 15 00:01:13,620 --> 00:01:15,990 ‫That is what this is. 16 00:01:16,440 --> 00:01:23,160 ‫But over here, we have this color when we set this color to be equal to color. 17 00:01:23,400 --> 00:01:27,080 ‫What we're actually doing is changing the color that is up here. 18 00:01:27,090 --> 00:01:30,360 ‫That's what this color is. 19 00:01:30,810 --> 00:01:38,100 ‫And I'm going to talk a little bit more about the key word, this in this video, but I'll talk about 20 00:01:38,100 --> 00:01:42,780 ‫it in more depth when we get to the constructor for link lists. 21 00:01:43,260 --> 00:01:46,470 ‫But the thing I'll talk about here is the keyword. 22 00:01:46,470 --> 00:01:53,880 ‫This refers to a specific instance of whatever you're creating, in this case, a cookie. 23 00:01:54,300 --> 00:02:00,690 ‫So now that we've written this code, we can actually create a new cookie like this. 24 00:02:01,200 --> 00:02:07,650 ‫We're going to call our cookie cookie one and we're going to set it equal to new cookie and we'll pass 25 00:02:07,650 --> 00:02:09,600 ‫it the color green. 26 00:02:10,050 --> 00:02:13,500 ‫So let's walk through this line of code. 27 00:02:13,980 --> 00:02:17,400 ‫So our variable name is Cookie one. 28 00:02:17,670 --> 00:02:20,600 ‫So notice that this is a pointer to a cookie. 29 00:02:20,610 --> 00:02:22,170 ‫This is how it's going to work. 30 00:02:22,170 --> 00:02:29,790 ‫Whenever you create an object with a class, whatever variable that you set equal to that object that 31 00:02:29,790 --> 00:02:33,420 ‫you've created will be a pointer to that object. 32 00:02:33,900 --> 00:02:38,070 ‫And in this case, that object is a cookie. 33 00:02:38,610 --> 00:02:41,130 ‫We also have this new keyword. 34 00:02:41,130 --> 00:02:47,760 ‫The new keyword will make it where we run the constructor, and we're going to pass that constructor 35 00:02:47,760 --> 00:02:49,230 ‫the color green. 36 00:02:49,440 --> 00:02:54,240 ‫And when we do all of this, it will create a green cookie. 37 00:02:54,660 --> 00:03:02,430 ‫So you could say that this cookie, this one right here has the color green. 38 00:03:03,030 --> 00:03:09,240 ‫So that keyword this is referring to this specific instance of cookie. 39 00:03:09,690 --> 00:03:14,540 ‫And so to make that point more clear, let's create another instance of cookie. 40 00:03:14,550 --> 00:03:20,550 ‫We'll call this one Cookie two, and we'll make this one blue. 41 00:03:20,940 --> 00:03:24,000 ‫So we have a different variable name cookie to. 42 00:03:24,770 --> 00:03:27,650 ‫And we've made this one blue. 43 00:03:28,160 --> 00:03:35,660 ‫This particular instance of Cookie that we're calling Cookie two is going to be blue. 44 00:03:36,170 --> 00:03:45,590 ‫So let's drop these cookies out of here and expand this cookie class so we can create other member functions 45 00:03:45,590 --> 00:03:46,610 ‫in the cookie class. 46 00:03:46,610 --> 00:03:55,010 ‫So we could do something like get color that returns the color for a particular instance of cookie. 47 00:03:55,250 --> 00:04:03,020 ‫Then we can also do something like set color that is going to change the color for a particular instance 48 00:04:03,020 --> 00:04:03,890 ‫of cookie. 49 00:04:04,190 --> 00:04:10,310 ‫So let's bring back these two lines of code that actually create our two cookies and we'll look at all 50 00:04:10,310 --> 00:04:12,740 ‫of this and VTS code. 51 00:04:13,480 --> 00:04:17,410 ‫So there is our cookie class that we just created there. 52 00:04:17,980 --> 00:04:19,990 ‫And then I'm going to scroll up here. 53 00:04:20,350 --> 00:04:27,010 ‫And our main function contains those two lines that create cookie one and Cookie two. 54 00:04:27,550 --> 00:04:34,630 ‫And then with these two lines, we'll print out the color of cookie one and cookie two. 55 00:04:35,440 --> 00:04:42,310 ‫So I'll run this and you can see that cookie one is green and cookie two is blue. 56 00:04:42,940 --> 00:04:52,210 ‫But if I come up here and I paste in this line, we're going to set the color of cookie one to be yellow. 57 00:04:52,660 --> 00:04:57,970 ‫So now when we run these two lines, we'll expect cookie one to be yellow, but cookie two to still 58 00:04:57,970 --> 00:04:59,380 ‫stay blue. 59 00:04:59,890 --> 00:05:01,150 ‫And I'll run this. 60 00:05:01,660 --> 00:05:07,630 ‫And you can see that we've changed the color of cookie one to yellow, but cookie two still stays blue. 61 00:05:08,020 --> 00:05:14,980 ‫And the reason for that is when we did the set color, we only did it to the instance of Cookie that 62 00:05:14,980 --> 00:05:16,870 ‫we're calling Cookie one. 63 00:05:17,440 --> 00:05:19,570 ‫So now let's flip back. 64 00:05:20,080 --> 00:05:27,850 ‫So what we've created so far is a class and cookie one, which is now yellow, and then cookie two, 65 00:05:27,880 --> 00:05:29,710 ‫which remains blue. 66 00:05:30,220 --> 00:05:34,450 ‫So then the question becomes, how are we going to use this in the course? 67 00:05:34,720 --> 00:05:40,300 ‫So an example of where we'll use it will be when we create a linked list. 68 00:05:40,630 --> 00:05:46,720 ‫We'll have a constructor for our linked list, which is going to be the same name as the class, but 69 00:05:46,720 --> 00:05:50,120 ‫we'll create other member functions as well. 70 00:05:50,140 --> 00:05:57,100 ‫So for example, we'll create a member function that will append a node of a particular value to the 71 00:05:57,100 --> 00:05:58,420 ‫end of the length list. 72 00:05:58,630 --> 00:06:06,010 ‫And then we'll write another function to remove the last item in the list, and one to pretend a value 73 00:06:06,010 --> 00:06:14,290 ‫to the beginning of the link list, or to insert a node with a particular value at a particular index, 74 00:06:14,710 --> 00:06:18,190 ‫or to remove a value at a particular index. 75 00:06:18,640 --> 00:06:24,340 ‫So in the next section, when we create length lists, we'll create all of these member functions and 76 00:06:24,340 --> 00:06:25,330 ‫a few more. 77 00:06:25,990 --> 00:06:28,780 ‫And that is our quick overview. 78 00:06:29,560 --> 00:06:30,730 ‫Of classes.