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So we left off here last time and what we did was we created this nice render template test function



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to actually go and pass all of our templates, including the layouts, and store them in this variable.



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My cache and my cache is a map and I can look up values in that map by a string and the string in this



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case, the thing I look up values in the map by happens to be the name of the template.



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So something like about page temple or homepage dot temple.



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And once I look them up I actually get a pointer to that ready to use template, which is exactly what



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I need to render pages to the site.



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So this actually creates that cache, that, that map that I can use that I need to be able to use.



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Where can I use that?



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Well, the logical place to use that, of course, is here in this render template function.



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But the first thing I'm going to do is get rid of all of this code that did nothing more than show that



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that that we were building the cache properly.



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That's of no value to us.



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So let's get rid of it so we can get rid of that there.



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And then I have to re initialize error because it's the first time I'm using it and there's a line down



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here where I can get rid of that as well.



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All right.



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So we're I mean, this is the logical place to use that map of of templates, our template cache.



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So I need to get this value that's produced right here, up here.



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So the obvious thing to do is to call this function.



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But first, let's give it a more meaningful name rather than calling it render template test, which



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is not a great name.



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Let's call it create template cache.



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And I'm not ever using this response rate or as a parameter, so I'm going to delete that for now.



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I might need it later on.



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If I do, I'll add it back in.



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So up here, I probably should give this a comment.



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So let's do that now to get it out of the way.



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Creates a template cache as a map.



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All right, I need called here.



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That's all I need to do.



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And this takes no parameters now because we got rid of the response rate and it returns a map and an



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error.



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So it returns to things.



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So let's just call it simple enough.



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We'll call our template cache T.C. and we'll check for an error.



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And that's a sign the value of create template cache.



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And then we have to check for an error.



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If error is not equal to nil, then I actually want to die at this point.



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And there's better error handling we'll be looking at later on.



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But for this, for the purposes of what we're trying to do right now, we're just going to die.



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So I'll say log fatele and an error.



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And that stops the application at this point because we can't get our template cache, therefore we



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can't show any pages.



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There's no point in going any further.



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So assuming we get past this, which we will because we know this works, how are we going to actually



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do something with an individual template when we pull that value out of the map?



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So I could just say my template is equal to and and pull it out of the map.



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So my map is called T.C. and I could pull the template name, which we know is called Tapio, the variable



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here, so we could copy that and paste it in here and that will actually work.



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But what if the template I'm trying to pass doesn't exist?



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So I'm passing it instead of passing about page up to Templer home page that template.



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What if the parameter is something like Yellow Pages template, which doesn't exist anywhere in the



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map?



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Well, one of the very common ways of checking for this sort of thing is actually to assign to variables



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here.



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So what will happen is if the template I'm trying to pull out exists, then TI will have a value and



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this will be set to true.



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But if it doesn't exist, this won't have any useful value and this will be default.



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So I can, this will be set defaults so I can check for that by saying if not OK then what I want to



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do.



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Well if I can't find the template again for the purposes of what we're doing right now, I'm just going



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to die.



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So if we get past this, then we have our template cache.



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If we get past this, then we have the template we want to use.



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So how do we use a template that's not read from disk?



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What we were doing before down here and all of this stuff we're going to get rid of very shortly is



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we actually read the template from the disk, then we pass the template and we're done.



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In this case, we can't do that.



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And we can't do that for a very simple reason because we haven't read it from disk.



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So we need to handle a little bit differently.



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And what I'm going to do here is create something called a bytes buffer, and I'm going to give it a



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name and that's going to be assigned the value of new bytes dot buffer.



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So this is a buffer that will hold the information.



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All of this can do is hold bytes.



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And I need to put that value, that PERS template that I currently have in memory into some bytes.



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So all I'm going to do is very similar to what we did before.



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I'm going to not check for an error at this point equals t my template.



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Execute.



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And I'm going to execute.



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To the buffer, the value of that template somewhat taking saying take this template that I have executed,



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don't pass it any data and store the value in this buff variable.



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Now, I have exactly what I need to write to my response writer so I can just say Buffer.



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Right.



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Try that again, Buff Dot.



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Right.



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And I'm going to write to my response writer, and that should write everything to the template, which



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means I can get rid of this.



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Now, this if I look at right to what is it written, it actually returns an error.



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So technically I should say error equals and then check for that error.



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If error is not equal to nil, then and I can just print the error.



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What do I have here now?



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It gets two returns.



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And what does it return?



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It returns and oh yes, the number of bytes and I don't care about the number of votes, so I'll get



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rid of that.



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Just ignore it.



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And if there's an error at this point, I don't want the application to die.



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I'm just going to write to the airlock.



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So I'll just say format the print line error writing template to browser followed by the error.



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All right.



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In theory, this should work because I've clean things up a little bit.



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And again, we're going to do improved error handling later on.



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But right now, I just want to get templates written to the screen.



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So let's try this.



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Let's open our terminal, clear the screen and go run command web.



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Start up, go.



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Let's see if it runs.



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That looks good.



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Let's go over to our Web browser and I'm on localhost eighty eighty in the last time I was here.



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Just give me a blank screen.



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So this time I hope to see the homepage and there it is.



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Now what about going to the about page.



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That's good as well.



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That's perfect.



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OK, it's almost perfect because if you think about it, we've actually although we're now using layouts



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and you can see that the layout is working properly.



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And if I view the source from the actual page, this part comes out of the layout document.



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This part comes out of the layout document.



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And this is the only thing that's being rendered from the about template.



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So this text here is exactly what I see here.



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So everything seems to be working, but let's look at our code again.



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Render Dutko.



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Here we are.



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What are we really doing every single time we go to the to render any page on the site?



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This function is getting called render template and it receives a response writer and it receives the



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name of the template I want to render.



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Then every single time we open a page on the site, we're building this template cache that seems really



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inefficient.



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Before we made these changes, we were just loading a single template, parsing it and writing it to



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the to the screen, to the browser window.



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But now every single time we render a single page on the site, we're actually parsing all of our template



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files.



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Now, go is very fast and you're not going to notice this if you don't have any appreciable amount of



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traffic on your site.



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But it is grossly inefficient and there's got to be a better way to do this.



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So in the next lecture, we'll figure out a better way to do that.