1 00:00:01,020 --> 00:00:06,900 So we're looking for a way to avoid loading the template, cash, the entire cash every single time 2 00:00:06,900 --> 00:00:12,360 we display a page on the site and what we're really talking about is setting configurations, because 3 00:00:12,360 --> 00:00:18,660 I want to set the configuration such that once I have this template set, I never want to load it again 4 00:00:18,660 --> 00:00:24,180 until the application restarts or I issue a command that says load the template cache again for whatever 5 00:00:24,180 --> 00:00:24,550 reason. 6 00:00:25,230 --> 00:00:31,440 So in order to do that, we effectively need to set up some kind of application wide configuration setting. 7 00:00:31,890 --> 00:00:35,100 Now, a very common method of doing this and other programming languages. 8 00:00:35,460 --> 00:00:36,660 Unfortunately, it's common. 9 00:00:36,660 --> 00:00:42,420 It shouldn't be is to use global variables to have variables that are available to every every part 10 00:00:42,420 --> 00:00:44,840 of the application at all times, no matter what. 11 00:00:45,360 --> 00:00:47,470 Well, we're going to use a slightly better approach. 12 00:00:47,490 --> 00:00:49,610 I'm going to do that by creating a new package. 13 00:00:49,890 --> 00:00:51,000 So I'm going to go to package. 14 00:00:51,360 --> 00:00:53,380 And the reason I'm I'll tell you why I'm creating it. 15 00:00:53,400 --> 00:00:54,900 This in its own package at the moment. 16 00:00:55,380 --> 00:01:03,080 I want to create a new folder and I'm going to call that config config. 17 00:01:03,570 --> 00:01:09,980 And inside of that, I'll create a new go file and I'll just call that config go. 18 00:01:10,650 --> 00:01:12,720 So it creates a new package. 19 00:01:13,140 --> 00:01:20,460 And the reason I'm going to create a package here is this configuration file might be accessed from 20 00:01:20,460 --> 00:01:21,690 any part of my application. 21 00:01:22,260 --> 00:01:30,360 And I'm going to be very careful to ensure that this configuration file doesn't import anything other 22 00:01:30,360 --> 00:01:32,130 than what it absolutely has to. 23 00:01:32,160 --> 00:01:38,100 What I'm trying to avoid is having applications by application set up such that packages in part from 24 00:01:38,100 --> 00:01:42,420 each other all over the place without regard to any kind of logic whatsoever. 25 00:01:42,750 --> 00:01:47,430 And the danger of doing that is you're going to run into something called an import cycle and your app 26 00:01:47,430 --> 00:01:48,930 will not compile. 27 00:01:49,230 --> 00:01:52,440 And that can be an extremely difficult error to avoid. 28 00:01:52,890 --> 00:01:59,400 So what I'm going to make sure here is that this package is imported where it needs to be by other parts 29 00:01:59,400 --> 00:02:00,240 of the application. 30 00:02:00,240 --> 00:02:05,850 So config is imported by other parts of the application, but it doesn't import anything else from the 31 00:02:05,850 --> 00:02:06,780 application itself. 32 00:02:06,780 --> 00:02:09,350 It only uses things that are built into the standard library. 33 00:02:09,570 --> 00:02:11,830 And this will help me avoid that kind of problem. 34 00:02:12,390 --> 00:02:13,500 So what am I going to do here? 35 00:02:13,500 --> 00:02:16,740 I am going to this is going to consist of a single struct. 36 00:02:16,740 --> 00:02:17,820 It's a type actually. 37 00:02:18,270 --> 00:02:23,790 It's a type called app config, which I'll name properly config. 38 00:02:24,090 --> 00:02:25,380 And it's just a struct. 39 00:02:25,380 --> 00:02:28,660 It's just a structure that holds certain kinds of information. 40 00:02:28,980 --> 00:02:32,460 And right now, all I want to put in there is my template cache. 41 00:02:32,670 --> 00:02:34,320 So I'll call it template cache. 42 00:02:34,320 --> 00:02:37,260 And I gave it a capital letter is the beginning part of the name. 43 00:02:37,260 --> 00:02:42,510 So that is visible and it's of type exactly the type that we have for our template cache. 44 00:02:42,510 --> 00:02:50,940 It's a map of string for the index and the content of each entry is a pointer to a template dot template. 45 00:02:52,080 --> 00:02:52,740 And there it is. 46 00:02:52,920 --> 00:02:57,000 So now I've created this now because this is something that should be commented. 47 00:02:57,000 --> 00:02:57,990 Let's give it a comment. 48 00:03:00,750 --> 00:03:04,860 Holds the application config. 49 00:03:05,620 --> 00:03:06,030 All right. 50 00:03:06,190 --> 00:03:07,200 A special application. 51 00:03:07,200 --> 00:03:07,470 Right. 52 00:03:09,050 --> 00:03:13,680 So I've created this and I'm not using anywhere right now, but I've created it. 53 00:03:13,680 --> 00:03:20,010 And because of the struct, I can put all kinds of things in here, anything I need site wide for my 54 00:03:20,010 --> 00:03:22,230 application, any kind of configuration setting. 55 00:03:22,350 --> 00:03:28,170 I can just add an entry to app config and it will be available to every package that imports this particular 56 00:03:28,170 --> 00:03:28,710 package. 57 00:03:29,580 --> 00:03:30,960 So I've created it. 58 00:03:31,110 --> 00:03:37,160 Now let's go back to may not go our very start of our application and let's get this going. 59 00:03:37,200 --> 00:03:38,970 So I'm going to create a variable here. 60 00:03:38,970 --> 00:03:44,880 Very first thing in my main function is to create a variable called app and it's going to be a type 61 00:03:44,880 --> 00:03:46,680 config app config. 62 00:03:47,490 --> 00:03:51,600 And you notice what I did that it imported it up here as it should, and it gives me the warning. 63 00:03:51,600 --> 00:03:56,020 You're not using this anywhere, so I'm not going to compile until you actually do something with it. 64 00:03:57,540 --> 00:04:02,980 So now that I've got that done, how do I actually get my template cache where it is? 65 00:04:03,000 --> 00:04:06,960 Well, right now, back into render, we're calling it right here, create template cache. 66 00:04:06,960 --> 00:04:09,540 And I don't want to do that here anymore, so I'll get rid of that in a minute. 67 00:04:09,540 --> 00:04:13,460 Instead, I want to call it here in main go. 68 00:04:13,890 --> 00:04:15,100 So can I do that? 69 00:04:15,120 --> 00:04:16,230 Well, let's find out. 70 00:04:16,620 --> 00:04:20,400 Let's say let's first of all see what that returns. 71 00:04:20,490 --> 00:04:26,900 So template cache right here returns a map of string, template, template and an error. 72 00:04:27,150 --> 00:04:31,260 OK, so let's let's try see if we can get one. 73 00:04:32,730 --> 00:04:39,330 I'm going to go over here and say my template cache and an error is equal to and that's stored in the 74 00:04:39,330 --> 00:04:44,670 package render rendered ago a render that create template cache. 75 00:04:45,480 --> 00:04:45,900 All right. 76 00:04:45,900 --> 00:04:48,900 So I've now created these variables. 77 00:04:48,930 --> 00:04:50,100 I should test for my error. 78 00:04:50,100 --> 00:04:55,350 If error is not equal to Neil, then logged fatal because I can't load it. 79 00:04:55,350 --> 00:04:59,760 So I want to dialogued up fadhel cannot. 80 00:05:00,420 --> 00:05:04,840 Create template cash, so that's fine. 81 00:05:06,000 --> 00:05:13,740 Now I've got the template cash, let's start in the app app template cash equals Terzieff and that all 82 00:05:13,740 --> 00:05:16,530 should compile, so let's make sure it actually runs. 83 00:05:16,580 --> 00:05:23,220 Make sure that everything's actually going to compile, go run command web. 84 00:05:23,570 --> 00:05:25,620 Mean Dutko or start go. 85 00:05:28,810 --> 00:05:33,220 Yet the comp. Let's go over to our Web browser and make sure things still work, we're not using that 86 00:05:33,220 --> 00:05:33,890 configuration. 87 00:05:33,910 --> 00:05:34,250 Yes. 88 00:05:34,270 --> 00:05:36,020 So it actually works the way that it should. 89 00:05:36,220 --> 00:05:36,930 No problem. 90 00:05:37,090 --> 00:05:37,530 Perfect. 91 00:05:38,080 --> 00:05:41,660 So I've created that template cache I started in my application. 92 00:05:41,950 --> 00:05:48,190 Now I want to use what's stored in this application, this this site wide config. 93 00:05:48,430 --> 00:05:54,100 I want to use that over in my render function instead of rendering the template the way that I am here 94 00:05:54,100 --> 00:05:59,140 by calling this template cache, I want to somehow let's put a comment in here to say what we're going 95 00:05:59,140 --> 00:05:59,560 to do. 96 00:06:01,710 --> 00:06:05,740 Yet the template cash from the app config. 97 00:06:06,570 --> 00:06:07,470 That's what I want to do. 98 00:06:07,560 --> 00:06:12,140 So this is all going to go away and then the rest of it will stay pretty much the same. 99 00:06:12,150 --> 00:06:15,490 I just don't want to create the template cache every single time I do this. 100 00:06:15,930 --> 00:06:19,950 So how do I get in this render template function? 101 00:06:20,130 --> 00:06:21,740 How do I get that app config? 102 00:06:21,750 --> 00:06:29,430 In other words, this thing I've created over here, this app which is of type config and currently 103 00:06:29,430 --> 00:06:36,090 only holds the template cache, how do I get it from here where I've created it over to here where I 104 00:06:36,090 --> 00:06:36,880 need to use it. 105 00:06:37,260 --> 00:06:40,200 Well we'll do that in the next lecture and it's a pretty straightforward process.