1 00:00:04,490 --> 00:00:05,540 ‫Hello and welcome. 2 00:00:05,540 --> 00:00:09,260 ‫In this lecture, we're going to be using variables to keep track of how much ammo we've got. 3 00:00:09,260 --> 00:00:15,140 ‫If you look in the top left corner, you can see that it's telling me the ammo value and each time I 4 00:00:15,140 --> 00:00:18,350 ‫fire it is decreasing that value. 5 00:00:18,350 --> 00:00:21,860 ‫Let's dive in and find out how variables help us do this. 6 00:00:22,460 --> 00:00:27,380 ‫So we're going to need variables in order to keep track of our ammo. 7 00:00:27,380 --> 00:00:28,700 ‫So what our variables? 8 00:00:28,700 --> 00:00:33,440 ‫Variables help us store, manipulate and refer back to information. 9 00:00:33,440 --> 00:00:37,640 ‫And most crucially for us, it's going to be that storage of the information. 10 00:00:37,640 --> 00:00:41,870 ‫So it's a bit like a box that we label as ammo. 11 00:00:41,870 --> 00:00:47,540 ‫And inside it we can put a value such as 20, which tells us how much ammo we've got left. 12 00:00:47,540 --> 00:00:49,820 ‫So each variable has to have a name. 13 00:00:49,820 --> 00:00:56,420 ‫It contains some data such as the data value 20 and crucially, each variable is of a particular type. 14 00:00:56,420 --> 00:01:03,020 ‫So in this case, the ammo box could be said to be an integer because it contains whole numbers. 15 00:01:03,020 --> 00:01:07,880 ‫You can't have half a piece of ammunition, so it makes sense for it to be an integer. 16 00:01:08,030 --> 00:01:13,010 ‫Now how would we go about creating a variable in blueprint? 17 00:01:13,010 --> 00:01:17,990 ‫So let's head over to our Blueprint panel and close down the details pane. 18 00:01:17,990 --> 00:01:19,550 ‫For some reason I have that open. 19 00:01:19,550 --> 00:01:21,500 ‫What we need is a different pane. 20 00:01:21,500 --> 00:01:27,680 ‫I'm going to go to the window menu and we're going to click on the My Blueprint element there. 21 00:01:27,680 --> 00:01:33,230 ‫And this is going to give us a new pane that allows us to add things to our blueprint that we couldn't 22 00:01:33,230 --> 00:01:34,220 ‫do before. 23 00:01:34,610 --> 00:01:38,120 ‫Here you can see there is a variables section and a little plus button. 24 00:01:38,120 --> 00:01:40,160 ‫So let's click the plus button, see what we get. 25 00:01:40,190 --> 00:01:42,530 ‫Okay, so we're starting to see what I told you. 26 00:01:42,560 --> 00:01:44,870 ‫We've got a name that we have to enter for our variable. 27 00:01:44,870 --> 00:01:46,220 ‫We're going to call it ammo. 28 00:01:46,220 --> 00:01:48,710 ‫And then next to that, we have a type. 29 00:01:48,710 --> 00:01:54,200 ‫You can see it's defaulted to it being of boolean type, but we can click a dropdown and we can see 30 00:01:54,200 --> 00:01:55,910 ‫all of the types available to us. 31 00:01:55,910 --> 00:01:57,890 ‫There's quite a few in our case. 32 00:01:57,890 --> 00:02:03,170 ‫We're just going to go for a straightforward, simple integer, like, so now what can we do? 33 00:02:03,200 --> 00:02:06,800 ‫How can we manipulate the value in this variable? 34 00:02:06,800 --> 00:02:09,590 ‫Well, for a start, it has a default value. 35 00:02:09,590 --> 00:02:13,790 ‫If you go over to the details pane which will close, but it has popped back up here. 36 00:02:13,910 --> 00:02:18,170 ‫You can see that it says please compile the blueprint to be able to set the default value. 37 00:02:18,170 --> 00:02:24,320 ‫So to compile the blueprints, we go to the toolbar and it's the leftmost button there is called compile. 38 00:02:24,320 --> 00:02:25,610 ‫It's got a little question mark to it. 39 00:02:25,610 --> 00:02:30,920 ‫I click compile and then it goes into a green arrow and now you can see that the default value can be 40 00:02:30,920 --> 00:02:31,250 ‫set. 41 00:02:31,250 --> 00:02:37,940 ‫So if I wanted to say have 20 ammo to start the game with, I can just type the value 20 in here and 42 00:02:37,940 --> 00:02:40,610 ‫that's going to be the value when we start playing. 43 00:02:40,610 --> 00:02:47,690 ‫But what if we want to update this as indeed we do want to update our ammunition value as we go through 44 00:02:47,690 --> 00:02:48,650 ‫playing the game? 45 00:02:48,770 --> 00:02:55,490 ‫Well, you can drag a variable from the my blueprint pane into your event graph, and when you do that 46 00:02:55,490 --> 00:02:56,990 ‫it gives you two options. 47 00:02:56,990 --> 00:03:04,070 ‫You've got the option to get the ammo, in other words, to get the value stored within it, or we've 48 00:03:04,070 --> 00:03:11,120 ‫got the value, the option to set the ammo which would allow us to overwrite the value that's currently 49 00:03:11,120 --> 00:03:11,720 ‫in there. 50 00:03:11,720 --> 00:03:14,000 ‫So let's have a look at what both these nodes look like. 51 00:03:14,000 --> 00:03:20,990 ‫And by the way, you can control drag a variable to get it and you can alt drag a variable to set it. 52 00:03:20,990 --> 00:03:28,430 ‫Now noteworthy is that the set needs to have some execution pins to tell it when to overwrite because 53 00:03:28,430 --> 00:03:34,380 ‫it does make a difference when you overwrite is going to have different effects on your gameplay, whereas 54 00:03:34,400 --> 00:03:39,410 ‫doesn't matter when you get a variable so it doesn't have any execution pins there. 55 00:03:39,410 --> 00:03:45,290 ‫And then you notice the key difference is that the getter only has an output data pin and the setter 56 00:03:45,290 --> 00:03:48,860 ‫has an input one so that you could set a different value. 57 00:03:48,860 --> 00:03:56,120 ‫And let me just show you that we can get the value of our ammo in Begin Play. 58 00:03:56,120 --> 00:04:01,970 ‫So at the end when we've done Welcome to Warehouse Wreckage, Get Ready to Rumble, we can put in a 59 00:04:01,970 --> 00:04:04,460 ‫new print for the ammo here. 60 00:04:04,610 --> 00:04:09,500 ‫So I'm going to drag off and create a new print string node. 61 00:04:09,500 --> 00:04:17,300 ‫And in here I'm going to control, click my variable and drag it into the scene and then connect up 62 00:04:17,300 --> 00:04:19,010 ‫my ammo to the print string. 63 00:04:19,010 --> 00:04:24,260 ‫It automatically adds in a little conversion node so that we can convert from the integer that's given 64 00:04:24,260 --> 00:04:27,260 ‫into the string that's required and we can hit play. 65 00:04:27,260 --> 00:04:33,830 ‫And sure enough, you can see the value 20 gets printed out there, meaning that our current ammo is 66 00:04:33,830 --> 00:04:34,970 ‫what we set it to. 67 00:04:35,090 --> 00:04:41,600 ‫Now I just want to show you one more piece of the puzzle here which would allow us to subtract ammo. 68 00:04:41,600 --> 00:04:47,060 ‫What we're going to have to do is after we have spawned our projectile and given an impulse, we're 69 00:04:47,060 --> 00:04:54,110 ‫going to want to, first of all, get the current ammo going, to want to subtract one from that ammo 70 00:04:54,110 --> 00:04:55,610 ‫and then set it back. 71 00:04:55,610 --> 00:05:00,260 ‫So there's three steps to it, but the step that we're missing is how do we subtract? 72 00:05:00,260 --> 00:05:04,010 ‫Well, if you right click anywhere in the event graph, you can. 73 00:05:04,090 --> 00:05:11,500 ‫Just search for subtract and it gives you this little deep default subtraction node which you can plug 74 00:05:11,500 --> 00:05:12,200 ‫anything into. 75 00:05:12,220 --> 00:05:16,660 ‫So if you plug in an integer, then it will expect an integer in the second pin as well. 76 00:05:16,660 --> 00:05:21,760 ‫So let me challenge you to subtract one from the value we've currently got in our variables. 77 00:05:21,760 --> 00:05:29,830 ‫So get the ammo value from the variable by using the control and drag to get a get node, then subtract 78 00:05:29,830 --> 00:05:36,580 ‫one from it using the subtract node, remembering to put one, put the getter into the input pin and 79 00:05:36,580 --> 00:05:39,100 ‫then just type in one into the other pin. 80 00:05:39,100 --> 00:05:46,420 ‫Then store it back in the ammo variable by dragging in a set node by doing an alt click and dragging 81 00:05:46,420 --> 00:05:52,600 ‫in the set node and finally print the result afterwards using a print string node and make sure that 82 00:05:52,600 --> 00:05:57,750 ‫all of your execution pins are connected up in the order we've just described. 83 00:05:57,760 --> 00:05:59,380 ‫Pause the video and have a go. 84 00:06:02,540 --> 00:06:03,110 ‫Okay. 85 00:06:03,110 --> 00:06:04,070 ‫Welcome back. 86 00:06:04,100 --> 00:06:11,690 ‫So first things first, we're going to control click in to get the ammo and we're going to plug that 87 00:06:11,690 --> 00:06:14,420 ‫into the first pin of our Subtract node. 88 00:06:14,420 --> 00:06:18,740 ‫And you notice that then the second pin becomes green as well and allows us to enter a value. 89 00:06:18,740 --> 00:06:20,240 ‫I'm going to enter the value of one. 90 00:06:20,240 --> 00:06:23,300 ‫So I've got the ammo value, subtracting one from it. 91 00:06:23,300 --> 00:06:26,870 ‫So the output is going to be the current ammo minus one. 92 00:06:26,870 --> 00:06:33,230 ‫So initially it will be 20, then it will be 18, etc. etc. Then with their output value, I want to 93 00:06:33,230 --> 00:06:40,850 ‫set my ammo so I'm going to click the ammo and drag it in and then I'm going to connect up the output 94 00:06:40,850 --> 00:06:43,490 ‫pin from the subtraction to the input pin of the set. 95 00:06:43,490 --> 00:06:50,210 ‫And then I need to connect up the execution pins so that the set happens after add impulse. 96 00:06:50,210 --> 00:06:57,080 ‫And then I can take the output value from set if I want to or the output value from the subtraction. 97 00:06:57,080 --> 00:07:04,430 ‫Either one of these will be the same and I can feed that in to a print string node or I can't do it 98 00:07:04,430 --> 00:07:08,780 ‫directly into a print string node because it doesn't know that I can do the conversion. 99 00:07:08,780 --> 00:07:15,260 ‫So I need to pull in a print string node, then connect up the output pin from set to the input pin 100 00:07:15,260 --> 00:07:20,990 ‫of that print string and move around by conversion node and connect up the execution pins. 101 00:07:20,990 --> 00:07:27,170 ‫Now if I go ahead and hit play, you can see it says My ammo is 20 and if I shoot, my ammo goes down 102 00:07:27,170 --> 00:07:31,070 ‫to 19, 18, 17 and so on. 103 00:07:31,070 --> 00:07:36,410 ‫I can keep shooting until I get down to zero, but I can keep going. 104 00:07:36,410 --> 00:07:42,350 ‫I can go into the negative numbers here because there's nothing in my code that tells me to stop. 105 00:07:42,350 --> 00:07:45,260 ‫Well, we'll figure that one out in the next lecture. 106 00:07:45,260 --> 00:07:46,070 ‫I'll see you there.