1 00:00:04,400 --> 00:00:05,210 ‫Hello and welcome. 2 00:00:05,210 --> 00:00:10,100 ‫In this lecture, we're going to be looking at a special function called the constructor that allows 3 00:00:10,100 --> 00:00:13,790 ‫us to give default values to properties in our class. 4 00:00:13,790 --> 00:00:16,820 ‫And we'll see when it's called in the editor. 5 00:00:16,820 --> 00:00:18,890 ‫Let's dive in and find out. 6 00:00:19,430 --> 00:00:25,430 ‫Now, with this trigger component, I would like to add a tick component function in here so that we 7 00:00:25,430 --> 00:00:32,450 ‫could check which components, which other actors are currently overlapping this trigger component and 8 00:00:32,450 --> 00:00:37,010 ‫we could activate if it is the right kind of actor. 9 00:00:37,550 --> 00:00:39,890 ‫The problem is, well, we'll see what the problem is. 10 00:00:39,890 --> 00:00:41,870 ‫Let's try and implement a tick function. 11 00:00:41,870 --> 00:00:48,110 ‫If we go over to the grab H to see what the declaration of a tick component function should look like, 12 00:00:48,110 --> 00:00:50,690 ‫it needs to be in the public section. 13 00:00:50,690 --> 00:00:53,450 ‫It's a virtual void, tick component, delta time. 14 00:00:53,450 --> 00:00:56,000 ‫There's lots of parameters, so let's just copy it. 15 00:00:56,030 --> 00:01:04,430 ‫Go over to the tick component header, add it in underneath our begin play and then we're going to copy 16 00:01:04,430 --> 00:01:08,570 ‫that definition, take it over into our trigger component. 17 00:01:08,570 --> 00:01:13,280 ‫CP And one thing that we'll notice is there's a couple of key words here that we can remove. 18 00:01:13,280 --> 00:01:15,140 ‫We can remove the virtual keyword. 19 00:01:15,140 --> 00:01:17,030 ‫That's generally a rule that we can follow. 20 00:01:17,030 --> 00:01:19,430 ‫We can also remove the override keyword. 21 00:01:19,430 --> 00:01:22,040 ‫These are things that don't need to be in the C++ file. 22 00:01:22,190 --> 00:01:24,770 ‫We need to add the class name. 23 00:01:24,770 --> 00:01:26,330 ‫So you trigger component colon. 24 00:01:26,330 --> 00:01:27,380 ‫Colon. 25 00:01:27,830 --> 00:01:35,870 ‫Then we replace our semicolon with some braces and we need to make the call to the super tick component. 26 00:01:35,870 --> 00:01:43,220 ‫So because that's quite a long call, I'm going to copy it from our grab a CP and paste it in to this 27 00:01:43,220 --> 00:01:43,460 ‫one. 28 00:01:43,460 --> 00:01:49,040 ‫Now what this is doing is it's essentially calling the parent's tick component function. 29 00:01:49,040 --> 00:01:52,880 ‫So the parent in this case being our box component. 30 00:01:52,880 --> 00:02:00,050 ‫So it's important to call that in case there is any functionality there that needs to be used and enabled 31 00:02:00,050 --> 00:02:01,580 ‫for this component to work. 32 00:02:01,580 --> 00:02:06,890 ‫If we don't do that, we're essentially bypassing any of that functionality and things can break. 33 00:02:06,890 --> 00:02:12,980 ‫So very important to always remember to call to super when we are implementing begin, play and tick 34 00:02:12,980 --> 00:02:13,820 ‫component. 35 00:02:13,820 --> 00:02:17,750 ‫Now let's copy our log message from Begin Play and put it in tick component. 36 00:02:17,750 --> 00:02:25,040 ‫And instead of saying tick component logging and say Tick component is ticking in here and we're going 37 00:02:25,100 --> 00:02:30,740 ‫to go ahead and compile and see whether that tick is actually working once the compiler has finished, 38 00:02:30,740 --> 00:02:34,160 ‫let's go ahead and hit play, open up our output log and. 39 00:02:34,190 --> 00:02:37,400 ‫Hmm, well, nothing seems to be happening now. 40 00:02:37,400 --> 00:02:43,910 ‫The reason for this is that optimization wise, they automatically and unreal most components have their 41 00:02:43,910 --> 00:02:45,530 ‫tick switched off. 42 00:02:45,530 --> 00:02:49,880 ‫So actors usually have it switched on by default, but components usually have it switched off. 43 00:02:49,880 --> 00:02:54,890 ‫So in fact, if we look at some of the other components we've got such as our move that we know ticking 44 00:02:54,890 --> 00:02:58,610 ‫does work for, you can see that at the top of the file there is this. 45 00:02:58,610 --> 00:03:06,950 ‫You move a function and it's got this primary component tick dot B can ever tick equals true if you 46 00:03:06,950 --> 00:03:09,740 ‫don't set this property on the class. 47 00:03:09,740 --> 00:03:15,320 ‫So this is a property of the class as a property of the classical primary component tick and it is a 48 00:03:15,320 --> 00:03:19,340 ‫struct that has a B can ever tick property within it. 49 00:03:19,490 --> 00:03:28,490 ‫So what we're doing here is we are setting this default value on the mover class when we construct it. 50 00:03:28,490 --> 00:03:29,660 ‫That's what this function is. 51 00:03:29,660 --> 00:03:37,100 ‫It's called a constructor and it is a function that gets called whenever we create a new mover component 52 00:03:37,100 --> 00:03:42,950 ‫to automatically set default values, we can set some default values over in the header file like we've 53 00:03:42,950 --> 00:03:44,750 ‫done with should move move time. 54 00:03:44,750 --> 00:03:50,360 ‫But alternative to doing it over in the header file is that we can actually set these properties in 55 00:03:50,360 --> 00:03:51,800 ‫the constructor. 56 00:03:51,800 --> 00:03:57,350 ‫Now I'd like you to notice the syntax here we go over into the move a header file. 57 00:03:57,350 --> 00:04:03,320 ‫You can see that a constructor is named exactly the same as the class. 58 00:04:03,320 --> 00:04:11,720 ‫So the you mover is the class name for our mover component and its constructor is also called you mover 59 00:04:11,750 --> 00:04:12,350 ‫notice. 60 00:04:12,350 --> 00:04:14,630 ‫It has no return type either. 61 00:04:14,630 --> 00:04:19,490 ‫It doesn't make sense to return anything because we are constructing a new object. 62 00:04:19,490 --> 00:04:22,820 ‫We are just making this class happen. 63 00:04:22,820 --> 00:04:30,560 ‫So all we need is access to the properties of this class and also notice that it is set to public. 64 00:04:30,560 --> 00:04:35,180 ‫So it's in the public section of our class definition. 65 00:04:35,180 --> 00:04:39,470 ‫So I'd like to challenge you to enable ticking for yourself. 66 00:04:39,470 --> 00:04:44,720 ‫So you're going to create a constructor in the header and keep bearing in mind that syntax that we've 67 00:04:44,720 --> 00:04:52,130 ‫seen both in the mover H and the grab a lot of H, you're going to enable ticking as we've seen again 68 00:04:52,130 --> 00:04:54,620 ‫in those other components in their CP files. 69 00:04:54,620 --> 00:04:57,140 ‫So just you can copy how that's being done. 70 00:04:57,290 --> 00:05:02,450 ‫You can log from the constructor as well to try and see when does it get called? 71 00:05:02,450 --> 00:05:03,610 ‫Is it like begin play? 72 00:05:03,780 --> 00:05:07,290 ‫Or does it get called before begin play or what? 73 00:05:07,320 --> 00:05:09,840 ‫Go and pause the video and have a go. 74 00:05:12,920 --> 00:05:13,310 ‫Kay. 75 00:05:13,310 --> 00:05:14,100 ‫Welcome back. 76 00:05:14,120 --> 00:05:21,320 ‫So we're going to go in to our trig components, which are going to create a new public section in here. 77 00:05:22,070 --> 00:05:26,630 ‫We're remembering the colon at the end and then we need to call it exactly the same as the class. 78 00:05:26,630 --> 00:05:28,040 ‫So that's not trigger component. 79 00:05:28,040 --> 00:05:33,320 ‫It's not you trigger it is you trigger component in full. 80 00:05:33,320 --> 00:05:39,770 ‫And then we don't have any arguments to this constructor, so we put just empty parentheses and then 81 00:05:39,770 --> 00:05:41,600 ‫a semicolon at the end of the line. 82 00:05:41,600 --> 00:05:46,880 ‫Now we can go over to the CPP file and we can make the implementation here. 83 00:05:46,880 --> 00:05:48,290 ‫Again, we don't need a return type. 84 00:05:48,290 --> 00:05:57,560 ‫So it's just you trigger component colon, colon, you trigger component a bit repetitive, but that's 85 00:05:57,560 --> 00:05:58,550 ‫the way it works. 86 00:05:58,550 --> 00:06:05,420 ‫Then we put some curly braces and in here we can do any of our set up code to give the default values 87 00:06:05,420 --> 00:06:07,280 ‫to the class instance. 88 00:06:07,280 --> 00:06:12,530 ‫So if we go over to the grab a CPP and have a look at what it's doing, you can see it's got its primary 89 00:06:12,530 --> 00:06:16,670 ‫component tick dot B can ever tick equal to true. 90 00:06:16,670 --> 00:06:17,840 ‫So let's type that out. 91 00:06:17,840 --> 00:06:23,540 ‫Primary component tick dot B can ever tick. 92 00:06:23,540 --> 00:06:31,520 ‫B is just a prefix we often use when things have a boolean type set equal to true with a lowercase t. 93 00:06:31,670 --> 00:06:38,720 ‫So because changes to a constructor don't always get properly propagated in live coding, I'm going 94 00:06:38,720 --> 00:06:39,980 ‫to close down the editor. 95 00:06:40,100 --> 00:06:46,400 ‫I'm going to rebuild from within Visual Studio code, then I'm going to relaunch from the EU project 96 00:06:46,400 --> 00:06:47,000 ‫file. 97 00:06:47,000 --> 00:06:52,160 ‫When that's done, I'm going to go ahead and hit play, have a look at our output log and sure enough, 98 00:06:52,160 --> 00:06:54,890 ‫we can see that the trigger component is ticking. 99 00:06:55,130 --> 00:07:00,230 ‫So I'm going to remove that log message because it's annoying and close down the output log in Visual 100 00:07:00,230 --> 00:07:04,460 ‫Studio code, remove this log message in the tick component. 101 00:07:04,460 --> 00:07:06,020 ‫We can see that it's working now. 102 00:07:06,410 --> 00:07:10,910 ‫And what we did want to do is do a log in our constructor. 103 00:07:11,720 --> 00:07:17,990 ‫So let's do a new log saying constructing, see if live coding can pick it up this time and then we're 104 00:07:17,990 --> 00:07:21,680 ‫going to go to our output log and have a look straight away. 105 00:07:21,680 --> 00:07:23,750 ‫Nothing showing up in here. 106 00:07:24,170 --> 00:07:28,370 ‫Well, if I go ahead and hit play, I have a look at my output log. 107 00:07:28,370 --> 00:07:33,980 ‫I can see the log message that the trigger component is alive and long in advance of this. 108 00:07:33,980 --> 00:07:39,020 ‫Actually, you can see that it is constructing way ahead when it's just creating the world. 109 00:07:39,020 --> 00:07:44,630 ‫It starts constructing very early before obviously begin play because we need to get the whole world 110 00:07:44,630 --> 00:07:46,400 ‫ready before we start playing. 111 00:07:46,400 --> 00:07:51,440 ‫So it happens when we hit play, but in actual fact it also happens in the editor. 112 00:07:51,440 --> 00:07:58,130 ‫So if I select some actor here and then add a component to it and add our trigger, then have a look 113 00:07:58,130 --> 00:07:59,300 ‫at my output log. 114 00:07:59,300 --> 00:08:03,050 ‫Then you can see the constructing message was actually printed. 115 00:08:03,050 --> 00:08:10,490 ‫So we need to be careful what we do in our constructors because they actually get called the C++ code 116 00:08:10,490 --> 00:08:14,540 ‫gets called just when we're editing, not even playing our game. 117 00:08:14,540 --> 00:08:20,000 ‫These objects are being created and therefore set up and therefore need to call their constructor. 118 00:08:20,090 --> 00:08:25,880 ‫I'm going to go ahead and delete the trigger again and clear up a little bit by removing our constructing 119 00:08:25,880 --> 00:08:30,170 ‫log message and our begin play log message as well. 120 00:08:30,170 --> 00:08:30,800 ‫Great stuff. 121 00:08:30,800 --> 00:08:37,430 ‫So in this lecture we've seen how we can set up our own components so that they are almost identical 122 00:08:37,430 --> 00:08:42,320 ‫to the ones created in the templates for scene components and ACT components, we've seen how to use 123 00:08:42,320 --> 00:08:47,720 ‫a constructor to give default values to properties in our class. 124 00:08:47,720 --> 00:08:49,610 ‫I'll see you in the next lecture.