1 00:00:03,730 --> 00:00:09,010 Okay, everyone, it's been a long time coming, but we're finally going to be adding our other questions 2 00:00:09,010 --> 00:00:10,050 to our quiz. 3 00:00:10,060 --> 00:00:13,810 And to do this, we're going to be using something called a list. 4 00:00:14,140 --> 00:00:15,610 So what is a list? 5 00:00:15,640 --> 00:00:20,910 Well, they're kind of like arrays, which we've already seen when we were storing our buttons. 6 00:00:20,920 --> 00:00:26,770 So if we consider the similarities to an array, a list is still a grouping of multiple variables of 7 00:00:26,770 --> 00:00:28,060 the same type. 8 00:00:28,150 --> 00:00:31,990 Each item stored within our list is still called an element. 9 00:00:32,049 --> 00:00:35,350 Each element can be accessed by its index number. 10 00:00:35,710 --> 00:00:38,560 And counting again starts at zero. 11 00:00:38,950 --> 00:00:43,490 So there are the similarities, and you may currently be thinking that they're virtually identical. 12 00:00:43,510 --> 00:00:50,650 But the big difference between a list and an array is that lists are mutable, meaning that we can change 13 00:00:50,650 --> 00:00:51,640 their size. 14 00:00:51,880 --> 00:00:56,790 So with an array, once it's created, we can't change the size by the list. 15 00:00:56,800 --> 00:00:59,770 We can add and remove items as much as we like. 16 00:01:00,160 --> 00:01:03,360 So let's look at the syntax of how to create a list. 17 00:01:03,370 --> 00:01:08,920 If we first consider the syntax for an array, then we can create a new array like this. 18 00:01:09,070 --> 00:01:12,460 But for a list, the syntax is slightly different. 19 00:01:13,030 --> 00:01:18,430 First, we're going to specify that we want a list, and then inside the angled brackets or chevrons, 20 00:01:18,430 --> 00:01:21,760 we're going to tell the list what type it's going to be storing. 21 00:01:21,760 --> 00:01:24,970 So in this example, we're storing a list of integers. 22 00:01:25,270 --> 00:01:31,360 We then have the name of our variable, which in this case is odd numbers, and then we can initialize 23 00:01:31,360 --> 00:01:35,620 this list by saying new list of type integer. 24 00:01:36,370 --> 00:01:39,010 So that's how we're going to be creating a new list. 25 00:01:39,010 --> 00:01:42,250 But now let's look at some useful methods that are going to come in handy. 26 00:01:42,790 --> 00:01:48,670 First of all, if we want to check the item count within our list, we can use list count. 27 00:01:48,670 --> 00:01:53,680 So this is very similar to the array length that we were using before. 28 00:01:54,280 --> 00:02:00,640 Next, if we want to check that an item exists within our list, we can use list DOT contains and then 29 00:02:00,640 --> 00:02:02,810 we can pass in the thing we're looking for. 30 00:02:02,830 --> 00:02:08,770 So with the example of storing our odd numbers, this would ask whether the number three currently exists 31 00:02:08,770 --> 00:02:09,729 in our list or not. 32 00:02:10,240 --> 00:02:15,490 If we'd like to add a new item, we can use list, add and then tell it what we want to add. 33 00:02:15,490 --> 00:02:21,670 So in this case, the number three, we can remove an item with list, remove and again pass in what 34 00:02:21,670 --> 00:02:27,190 we want to remove if it exists, if we don't know a specific value that's contained in our list and 35 00:02:27,190 --> 00:02:34,030 we just want to remove the item at a given index we could use list remove at and then passing the index 36 00:02:34,030 --> 00:02:35,050 that we're interested in. 37 00:02:35,050 --> 00:02:39,640 So in this case, remove at zero would remove the first element in our list. 38 00:02:40,060 --> 00:02:45,880 And finally, another good one to remember is list dot clear, which will completely empty our list. 39 00:02:46,150 --> 00:02:51,760 So with explanations out of the way, let's go ahead and create our list for our questions. 40 00:02:52,300 --> 00:02:57,640 However, before we go ahead and do that, there's one thing I want to change about our current code, 41 00:02:57,640 --> 00:03:01,750 and that's our current serialised field for our current question. 42 00:03:02,050 --> 00:03:06,850 Once we've created our list, we're no longer going to need this serialized in the inspector. 43 00:03:06,850 --> 00:03:11,560 So let's go ahead and clear things up by just removing that serialized filled attribute. 44 00:03:11,950 --> 00:03:17,230 And the other thing I want to do is actually rename this variable because our list is going to have 45 00:03:17,230 --> 00:03:18,730 a very similar name. 46 00:03:18,730 --> 00:03:24,580 And to avoid errors and confusion as we continue to code, let's go ahead and rename this by pressing 47 00:03:24,580 --> 00:03:29,380 F two and instead of question, let's call this the current question. 48 00:03:30,210 --> 00:03:35,520 With that renamed that should have replaced any instance of our old question with current question. 49 00:03:35,520 --> 00:03:39,390 So if we have a quick scroll down, we can see that in display answer. 50 00:03:39,390 --> 00:03:42,090 It's now looking at the current question instead. 51 00:03:43,180 --> 00:03:43,870 And in display. 52 00:03:43,870 --> 00:03:50,320 QUESTION We're also looking at the current question so minor code fixing aside, let's go back up to 53 00:03:50,320 --> 00:03:54,070 our variables and let's go ahead and create our list. 54 00:03:54,220 --> 00:03:57,430 We're going to want to drag over our questions in the inspector. 55 00:03:57,430 --> 00:04:05,080 So let's make this a serialized field and we can create a new list by saying list of type question. 56 00:04:05,080 --> 00:04:11,170 So, so our question, script table objects and we'll give this variable the name questions, which 57 00:04:11,170 --> 00:04:15,550 is why we wanted to change our old question variable to current question. 58 00:04:16,060 --> 00:04:20,320 Now, because this is serialized, we can go ahead and leave this as it is. 59 00:04:20,320 --> 00:04:25,660 But if you want some added protection in case you remove the serialized field later on in your journey, 60 00:04:25,660 --> 00:04:31,630 we can instantiate this list by writing equals new list of type question. 61 00:04:31,640 --> 00:04:38,170 So, so with our list set up and once we've dragged the questions over in the Inspector, we're going 62 00:04:38,170 --> 00:04:42,970 to need to get questions from this list and make them the current question. 63 00:04:43,420 --> 00:04:46,810 So let's scroll down to our get next question method. 64 00:04:47,410 --> 00:04:52,390 And now when we get a new question, we're instead going to want to get the question from our list. 65 00:04:52,720 --> 00:04:58,810 Now, there are many ways we may decide to get these questions from our list, but to add a bit of randomness 66 00:04:58,810 --> 00:05:02,830 to our game, I'm going to be pulling a random question out of our list. 67 00:05:02,830 --> 00:05:07,060 Whenever we need to get a new one, we're going to do this in a new method. 68 00:05:07,180 --> 00:05:12,820 So once we've set the button state and the button sprites, but before we display our question, let's 69 00:05:12,820 --> 00:05:16,480 go ahead and write a new method called Get Random Question. 70 00:05:17,650 --> 00:05:19,590 Then we're going to need to write this method. 71 00:05:19,600 --> 00:05:25,090 So underneath our next question, let's create a void, get random question method. 72 00:05:25,690 --> 00:05:27,850 Let's start by getting that random number. 73 00:05:27,850 --> 00:05:32,560 So we're going to have a temporary variable of type int called index. 74 00:05:32,860 --> 00:05:42,220 And this is going to be equal to random range with a minimum of zero and a maximum of our questions 75 00:05:42,640 --> 00:05:43,390 count. 76 00:05:43,390 --> 00:05:49,630 So this is going to return a random number between element zero of our list and the last element in 77 00:05:49,630 --> 00:05:50,260 our list. 78 00:05:50,530 --> 00:05:56,770 With that index, we can then say that our current question is going to be equal to the question in 79 00:05:56,770 --> 00:06:03,340 our list at that index, and then we want to go ahead and remove that question from the list so we can 80 00:06:03,340 --> 00:06:08,380 say questions, remove the current question. 81 00:06:09,520 --> 00:06:15,310 Now, this should all be fine, but whenever I remove an item from a list, it's always good to just 82 00:06:15,310 --> 00:06:21,220 double check that it actually exists to avoid any potential errors cropping up and just to err on the 83 00:06:21,220 --> 00:06:22,210 side of caution. 84 00:06:22,600 --> 00:06:27,220 This shouldn't strictly be necessary for our game because it is very small and we're not going to be 85 00:06:27,220 --> 00:06:29,710 doing much else with our questions list. 86 00:06:29,710 --> 00:06:34,330 But in larger projects, when we start moving things around and we have a lot of things talking to each 87 00:06:34,330 --> 00:06:40,210 other, it's always good to make sure this check happens so that we don't accidentally run into a problem 88 00:06:40,210 --> 00:06:42,310 that may cause our game to throw an error. 89 00:06:42,580 --> 00:06:51,490 And we can check to see that our current question exists in our list by saying If questions DOT contains 90 00:06:52,480 --> 00:06:57,340 the current question, then we want to go ahead and remove it. 91 00:06:57,610 --> 00:07:03,220 Now, with that set, let's go ahead and save our script and jump over into Unity to test it all out. 92 00:07:03,940 --> 00:07:09,670 If we look in the inspector under our questions header, we now have a list of questions that we can 93 00:07:09,670 --> 00:07:10,150 use. 94 00:07:10,360 --> 00:07:16,240 So let's lock the inspector so that we can drag our questions over and over to the questions folder 95 00:07:16,240 --> 00:07:23,110 where we stored all of our script objects and then select all of them and drag them over into our list. 96 00:07:23,560 --> 00:07:28,270 Now for me, that's put them in reverse order, but because I'm pulling them at random, it doesn't 97 00:07:28,270 --> 00:07:29,620 really matter too much. 98 00:07:29,620 --> 00:07:34,600 If you want to change the order of any of the elements, you can just click and drag to move them up 99 00:07:34,600 --> 00:07:35,350 or down. 100 00:07:36,880 --> 00:07:41,980 And if you want to add or remove any other element, then we can either use the plus and minus buttons 101 00:07:41,980 --> 00:07:45,880 at the bottom or we can change the size of our list with this input field. 102 00:07:46,210 --> 00:07:50,200 So questions all set up, we should now be picking questions at random. 103 00:07:50,350 --> 00:07:52,780 So let's go ahead and hit play to test this out. 104 00:07:53,410 --> 00:07:57,700 And before we go ahead and answer a question, I'm going to pause the game and click back on my quiz 105 00:07:57,700 --> 00:08:04,030 canvas so I can see the questions that are in our list, and we'll notice that two of them have actually 106 00:08:04,030 --> 00:08:06,250 been removed rather than just one. 107 00:08:06,640 --> 00:08:12,670 Now, the good news is the questions were randomly selected, but why did we remove two of them? 108 00:08:12,970 --> 00:08:17,560 Well, there's a very logical explanation for this, which we'll fix in just a moment. 109 00:08:17,560 --> 00:08:22,420 But for now, let's just do a little bit more testing to make sure that it doesn't happen for every 110 00:08:22,420 --> 00:08:23,440 single question. 111 00:08:24,420 --> 00:08:27,510 So let's unpause our game and wait for the timer to run down. 112 00:08:27,870 --> 00:08:32,159 And for all subsequent questions, it does look like it's just removing the one. 113 00:08:32,340 --> 00:08:38,070 So if we quickly skip through the rest of our quiz, well, notice that once we've answered the final 114 00:08:38,070 --> 00:08:44,730 question and our list is empty, then if we check the console, we're getting an error saying that the 115 00:08:44,730 --> 00:08:50,790 index was out of range, i.e. we're trying to pull an item out of a list when the list is empty. 116 00:08:51,090 --> 00:08:53,130 So two bugs to fix there. 117 00:08:53,130 --> 00:08:55,500 So let's jump back over into our script. 118 00:08:55,890 --> 00:09:02,400 And the first bug of removing two questions at once is incredibly simple to fix because if we head up 119 00:09:02,400 --> 00:09:08,700 to our start method, we're currently getting the next question in START and we don't actually want 120 00:09:08,700 --> 00:09:09,990 to be doing that anymore. 121 00:09:09,990 --> 00:09:14,310 So let's delete that line and also our commented outline as well. 122 00:09:14,490 --> 00:09:19,170 And that should fix the problem with two questions being selected on the first run through. 123 00:09:19,910 --> 00:09:25,490 And then to fix the error that comes up when we've run out of questions in our list, let's head down 124 00:09:25,490 --> 00:09:29,930 to our get next question method and we're going to put in a check here. 125 00:09:30,290 --> 00:09:33,260 And I think this would make a very good challenge for you. 126 00:09:33,830 --> 00:09:39,620 I want you to go ahead and modify our get next question method to check whether there are still questions 127 00:09:39,620 --> 00:09:43,820 left in our list before we go ahead and execute those other four methods. 128 00:09:43,820 --> 00:09:46,670 So pause the video now and give that one a go. 129 00:09:52,020 --> 00:09:52,410 Okay. 130 00:09:52,410 --> 00:09:53,310 Welcome back. 131 00:09:53,340 --> 00:09:55,620 So hopefully you got on well with that challenge. 132 00:09:55,620 --> 00:10:03,840 And the solution to this problem is going to be to use an if statement and ask if the questions dot 133 00:10:03,840 --> 00:10:06,600 count is greater than zero. 134 00:10:07,500 --> 00:10:11,070 Then we want to go ahead and run these four methods. 135 00:10:12,180 --> 00:10:18,050 So let's go ahead and test this out to see if everything's worked through the magic of video editing. 136 00:10:18,060 --> 00:10:21,630 We can find that both of these bugs have now been fixed. 137 00:10:21,630 --> 00:10:23,070 So congratulations. 138 00:10:23,070 --> 00:10:29,040 We now have a game with multiple questions and at this stage you can feel free to add as many other 139 00:10:29,040 --> 00:10:30,960 questions to your game as you like. 140 00:10:31,410 --> 00:10:36,030 Now, the next thing we're going to want to look at in our game is to improve the UI a little bit because 141 00:10:36,030 --> 00:10:41,340 we now have multiple questions, but the player has no idea how far through the game they are. 142 00:10:41,370 --> 00:10:45,300 But that's a topic for another lecture, so I'll see you there.