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So our task right now is to figure out how to get this app variable, which is an app config and app



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config, is nothing more than a struct that holds certain kinds of things we want to share with our



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application.



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We need to get that around to the parts of our application that have to have it.



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And right away, I can see there are two places that are going to need this app config.



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The obvious one is render.



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Render is going to have to have this because we don't want to recreate the template cache every time



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we build a page.



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So that's one place that needs to have it.



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And the other place that's going to have to have it, obviously, are the handlers and the handlers



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are going to have to have access to all kinds of configuration settings for the application.



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So let's do the render.



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First one I'm going to do here is I'm going to create a new function inside this render template, OK?



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And the render template is going to serve.



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The function is going to be called func new templates and it's going to take an argument.



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And the argument is going to take is a pointer.



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We'll call it a for the variable.



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It's going to be a pointer to config app config.



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Now I need to do something with that, a variable.



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So I'm going to create a new variable here called App and app is going to be a pointer to config app



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config.



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And when this function is called, it's just going to set that variable up equals, hey, that's it.



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Pretty straightforward.



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Let's give this thing a comment as we should create a new template.



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Sorry, let's just do this.



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Sets the config for the template package, not only the trick.



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OK, so I've got this function.



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I need to call it somewhere.



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Let's go back to Main Dutko and think about when we should call it.



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Well, we've created the app variable here.



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Then we get our template cache.



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Then we assign that to this.



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And now we want to call that new template cache so I can call two templates.



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Sorry, render create new templates, and that's going to take a pointer to app config, so I can't



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just put put app in there because that's not going to work.



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It wants a pointer instead.



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I want a reference to that there.



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So that will give our application the render component or the render package of our application access



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to this app config variable.



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So let's go back to our render routines and do something with this app variable right here.



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Instead of creating the template cache, let's just use it.



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So Tsay equals app dot template cache.



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You have to of course assign that not equal and that we can get rid of this.



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So if we did this properly, what should happen now is I should be able to run this application except



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I still have an error log.



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Fatal error.



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So if not, OK, log Fadal.



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Well we don't actually have an error here.



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I'll just say instead, log fatele could not create a template.



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You could not get a template from template cache.



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We'll just do that for now.



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Fixes that.



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And now down here we have to assign assign the error variable.



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Good.



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So that should take care of it all.



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Now we should be able to actually run this application and we'll create our template cache when the



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application starts.



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And then when we render a page, we're pulling the value from this application structure, our config.



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Let's see if that works.



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So we'll stop our application, go run command web Stargirl.



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It started.



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That's good.



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Let's go over to our Web browser and reload the homepage.



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And there it is.



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And let's go to the about page and there it is.



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Now, that is way more efficient.



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We're not accessing the disk to get the template every time we load the page.



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Instead, we build a map that holds all of our templates, put that in an application wide site config



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and we can render our templates.



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Well, that is a real improvement.



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Now, there's a lot more we can do with that configuration variable and we may as well do it now because



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we know that the handlers are also going to have to have access to it.



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They may not use the template cache, but we are going to put things in there that will make the application



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run much better because we can share configuration files.



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So how are we going to do that?



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Well, to start with, we're going to go to our handlers page and again create some new things.



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Now, this will seem a little odd to you to begin with.



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We're going to use something called we're going to use something called the repository pattern.



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It's a very common pattern that allows it allows us to swap components out of our application with a



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minimal changes required to the code base.



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It seems a little confusing at first, but hopefully by the time I go through it a couple of times,



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it will make sense to you to start with.



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I'm going to create a variable or a creative type first, and this is going to be a type it's going



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to we're going to have to give it a name.



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I shall call it repository, because it's the repository pattern and it is a structure.



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And all it's going to hold right now is an app, which is a type pointer to config app config.



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All right.



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So I've now imported that.



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I've created my type.



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So let's create a variable that uses that type VAR and I'm going to call this repo and I'm going to



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give it a capital letter.



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So it's visible outside of this package, which is critical.



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It's a type repository.



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So I've now created a variable that I'm not using with the type that I'm only using to initialize this



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variable or declare this variable.



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So now I need a couple of new things to start with.



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This is a function and I'm going to call it new repo, and it's going to take an argument.



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And the argument is I'll just give it the name of a because it is an application config.



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It's a type start, a pointer to config config, and it's going to return a pointer to a repository.



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All right.



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So to do that, all I have to do is return a reference to repo, the variable that I haven't done anything



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with yet.



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And I'm going to populate that with the only thing I have to put in that that type an app.



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Type of repository.



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An app and a sign of the value of, hey, that I passed right here in this perimeter, so now I have



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a function, new repo, OK, I'm not using it yet.



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I need one more function to create new handlers, funk, new handlers.



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And it's going to tape take an argument, ah, which is a type pointer to a repository and it doesn't



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return anything, it just sets a variable.



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And what it's going to set is the variable that I declared up here, repoll



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equals Perth.



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And let's give these things comments and we'll go through what they're supposed to do.



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This is a new handlers.



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It sets the repository for the handlers and this is new repo creates a new repository.



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And this is the type.



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Is the repository type and are variable.



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The repository.



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Used by the handlers, now, the only thing in a repository right now is actually the app config where



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we're going to put more things in here.



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For example, when we connect to databases, we need somewhere to share the database.



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Connection pool will share that using the repository structure, and it will make our life ever so much



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easier.



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So what's going to happen is, first of all, in my main function.



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I need to after I have declared my app variable, I need to set things up with our handlers and the



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very first thing I'm going to do is create a variable called repo that's going to call that function



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handler's new repo.



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And I'm going to pass it a reference to my app.



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OK, so that creates the repository variable.



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I'm not doing anything with that yet, but I'm out to after I create that repository variable, I pass



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it back to the handlers and create new handlers.



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So the handlers, new handlers and I'm going to pass it repels.



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And that should do the trick now, why on earth would I do this?



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If you think about it logically, I create a repository.



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Fine, so that calls new repoll.



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New report says take this app config that you just passed, appointed to the app config and populate



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the struct repository, return a new instance of this type that holds the application.



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Great.



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So I've done that in Maine and then I say I just take that thing I just created in handlers and I pass



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it back to handlers.



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So I call new handlers and new handlers actually just sets that variable repo, but I'm not using that



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anywhere.



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Well, actually, I'm going to and I'm going to use it in a very simple spot, one that will make sense



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to you momentarily.



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It does require a change to the functions themselves.



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And what I'm going to do is give these functions a receiver.



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And what it effectively does is links all of these functions, all of these handlers together with the



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repository.



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So all of the handlers have access to that repository.



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So I can do that simply by always seem to function.



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So far as func the keyword func that says I'm declaring a function, then the name just before the name



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in parentheses, I'm going to put a new variable, which I'm going to call em.



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I can call it whatever I want.



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But Amasa simple one letter thing that I don't have to do a lot of typing for and it's of type pointer



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to repository and then I'm going to copy that and paste it down here.



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Now these these both of these handlers and any other handlers I create that have this receiver have



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access to everything inside repository, which happens to be my application config.



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Now there's one more change I need to make before I can compile this and make it work, and we'll demonstrate



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that it does work.



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Over here in Maine, my handlers, my handler funk's don't work anymore and there's no reason why they



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don't work.



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Seems to be my handlers.



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I have a function called home.



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If I go over to handlers, sure enough, I have a function called home, but now I have a function with



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the receiver of type repo.



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So all that means is that I need to put dot repo in front of that.



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And repo in front of that, and now it should work and to demonstrate that it's going to work, let's



167

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pull something out of that configuration and have a look at it.



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Well, what do we have an app config right now?



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Well, we just have a template cache.



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I don't want to pull anything out of that.



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Let's just add a new structure to this and a new member to this.



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And I'm going to call it use cash and it's going to be of type, Wolf.



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So true or false?



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So now I've added this to the app config.



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So everything that refers to app config now has access to it.



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Let's go back to Mean Dudko.



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And just before we declare a repository, let's say app use cache equals false.



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I've now assigned the value of false to use cache and there's a reason for that.



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And let me show you what it is.



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We still have the application running, right?



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Let's make sure we do well on the about page.



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If I go look at the template for the about page and I'll bring up my templates here, find the templates



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00:12:02,050 --> 00:12:12,520

there's about if I make a change to this template, let's say we add P, this is a paragraph of text



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and save it and then go back to the about page and reload it.



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You would think that I would see that paragraph of text I just typed.



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00:12:20,530 --> 00:12:24,090

But I don't and I don't because I'm not reading it from the disk anymore.



187

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Remember, I'm pulling it from that template cache that we created.



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So what I'd like to be able to do is to say if you check the application preferences, so let's go to



189

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the render here.



190

00:12:36,550 --> 00:12:40,720

When I get the application preferences, I have access to the app here.



191

00:12:40,730 --> 00:12:42,640

Now I have access to the app variable.



192

00:12:42,640 --> 00:12:49,900

So let's say if I'm in development mode, not production, don't eat, don't use the template cache,



193

00:12:49,900 --> 00:12:51,990

instead rebuild it on every request.



194

00:12:52,000 --> 00:13:00,790

What I can do that really easily and I can do it by saying if app don't use cache, then pull the information



195

00:13:00,790 --> 00:13:01,270

out of that.



196

00:13:02,260 --> 00:13:03,740

Otherwise I want to read it.



197

00:13:03,910 --> 00:13:08,680

So what it's going to mean of course, is that I have to see what a template cache returns.



198

00:13:08,680 --> 00:13:10,570

It returns a map, string the string.



199

00:13:11,720 --> 00:13:16,330

So let's declare a variable just so I can get it outside of the scope of this.



200

00:13:16,480 --> 00:13:23,410

If statement var T.C. is of type that and then I'm not assigning, I'm really pulling it out.



201

00:13:24,070 --> 00:13:29,770

Otherwise, if it's false, T.C. equals create template cache.



202

00:13:32,680 --> 00:13:37,210

And that returns a template and a cache and an error error.



203

00:13:41,120 --> 00:13:43,460

Let's just ignore the air, you know, it works right now.



204

00:13:43,820 --> 00:13:46,270

OK, so what have I done now?



205

00:13:46,280 --> 00:13:50,950

I'm actually going to look in the configuration file and ask myself a simple question.



206

00:13:51,680 --> 00:13:54,080

First of all, I declare the variable this is going to hold my template.



207

00:13:54,080 --> 00:13:59,780

Cash, if used cash is true, then read the information from the template cache.



208

00:13:59,960 --> 00:14:02,120

Otherwise rebuild the template cache.



209

00:14:02,330 --> 00:14:05,490

And back in Maine, I said use cash defaults.



210

00:14:05,510 --> 00:14:10,520

So now if I start this up again, stop the application, start it up.



211

00:14:11,750 --> 00:14:14,600

Everything compiles and we look at the about page.



212

00:14:14,600 --> 00:14:17,750

It has this paragraph of text and I refresh the about page.



213

00:14:17,750 --> 00:14:19,190

OK, that's what I expect.



214

00:14:19,370 --> 00:14:24,440

And I would expect that whether you use cash was true or false because it's reading it right from the



215

00:14:24,440 --> 00:14:25,610

template cash that it built.



216

00:14:26,120 --> 00:14:32,600

But now because I'm in development mode, because I have this variable use, a used cash set defaults



217

00:14:32,810 --> 00:14:37,080

and because I have access to that in render, I can test against it.



218

00:14:37,250 --> 00:14:44,690

So now if I go back to my about page and add another paragraph of text and save it now, it should read



219

00:14:44,690 --> 00:14:47,930

it from the disk because I'm in development mode and there it is.



220

00:14:48,590 --> 00:14:49,110

All right.



221

00:14:49,490 --> 00:14:53,350

So this gives us a lot of control and a lot of power.



222

00:14:53,360 --> 00:14:58,970

It means that we can share information that parts of our application need really, really easily.



223

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If I need to add something to the application config, I just go to app config struct, create a new



224

00:15:04,370 --> 00:15:10,460

type, our new member for this this type, and it's immediately available to every other part of the



225

00:15:10,460 --> 00:15:12,890

application that might need to have access to it.



226

00:15:14,180 --> 00:15:15,050

That was a lot of work.



227

00:15:15,140 --> 00:15:18,990

Finally, in the next lecture, we're going to pass some data to templates.



228

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It's taken us a while to get here, but things are starting to shape up and they're starting to look



229

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good.