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09.

Turbo Drive

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It's day 9! Beautiful day 9 where we start to make our app shine. All the fundamentals are in place - AssetMapper, Tailwind & Stimulus - so today is... almost a victory lap. We're about to get a huge bang for our buck thanks to a library called Turbo.

Right now, our site, of course, has full page refreshes. Keep an eye on the logo in the address bar. When I click, everything is done with a full page refresh. That's fine. Never mind, that's not fine! I want our site to have a devastatingly great user experience.

Luckily, we have Turbo on our team: a JavaScript library forged from the depths of the internet, bent on destroying all full page refreshes. Watch on their site: you won't see any full page reloads as we navigate. And check out how fast that feels. It feels like a single page application, because, well, it is, it's just not one that we need to build with a frontend framework like React.

Installing Turbo

Like Stimulus, Symfony has a package that helps us work with this Turbo. Find your terminal, and run:

composer require symfony/ux-turbo

When that finishes, do:

git status

Like the other UX package, this modified controllers.json and importmap.php. In assets/controllers.json, it added two new controllers:

26 lines | assets/controllers.json
{
"controllers": {
// ... lines 3 - 12
"@symfony/ux-turbo": {
"turbo-core": {
"enabled": true,
"fetch": "eager"
},
"mercure-turbo-stream": {
"enabled": false,
"fetch": "eager"
}
}
},
// ... line 24
}

The first is... kind of a fake controller. It loads and activates Turbo - you'll see what that does in a moment - but it's not a Stimulus controller that we'll ever use directly. The second controller is optional - we're not going to talk about it, and it's disabled by default.

The other change, in importmap.php is, no surprise: it added @hotwired/turbo:

41 lines | importmap.php
// ... lines 1 - 15
return [
// ... lines 17 - 36
'@hotwired/turbo' => [
'version' => '7.3.0',
],
];

The result of this single command is amazing. When I refresh, watch the address bar: we're not going to see any more full page reloads! And everything feels super-duper fast. Uh, I love it. Even the forms! Click edit. Watch: this submits via AJAX. Or, if I go and create a new one, hit enter, that submits via AJAX. Our site just got transformed into a single page app with one command!

Turbo: What's the Catch?

You might be thinking:

This is too good to be true, Ryan. What's the catch?

Ok, there is a catch, but minor for new projects: your JavaScript must be written to work without full page refreshes. Historically, we've written our JavaScript to execute on page load... or run on document.ready. And those things just don't happen after the first page load. But as long as you have everything written in Stimulus, you're good.

For example: our celebrate controller: it doesn't matter how many pages I click around to, that just keeps on rolling.

If your app isn't ready for Turbo yet - because of the JavaScript problem - you can disable it. In app.js, import * as Turbo from '@hotwired/turbo'. Below, say Turbo.session.drive = false. I'm not going to do that... so I'll comment it out:

8 lines | assets/app.js
import * as Turbo from '@hotwired/turbo';
// ... lines 2 - 5
//Turbo.session.drive = false;
// ... lines 7 - 8

But why would I install Turbo... just to disable it? Because Turbo is actually three parts. The first is called Turbo Drive. That's the part that gives us free AJAX navigation on all link clicks and form submits. And that's what this disables.

But even if you're not ready for Drive, you can still use the two other parts: Turbo Frames and Turbo Streams. These are powerful and we'll spend a lot of time in this tutorial doing some wild things with them.

Turbo Drive itself is pretty simple, but it does have a few other tricks up its sleeve. And they're constantly adding new things. For example, one feature is called preloading. To show this off, go into templates/base.html.twig. If you're ever on a page... and you're really sure that you know what link the user is going to click next, you can preload that.

For example, on the "voyages" link, add data-turbo-preload:

52 lines | templates/base.html.twig
// ... lines 1 - 14
<body class="bg-black text-white font-mono">
<div class="container mx-auto min-h-screen flex flex-col">
<header class="my-8 px-4">
<nav class="flex items-center justify-between mb-4">
<div class="flex items-center">
// ... lines 20 - 27
<a href="{{ path('app_voyage_index') }}" data-turbo-preload class="ml-6 hover:text-gray-400">Voyages</a>
// ... line 29
</div>
// ... lines 31 - 36
</nav>
</header>
// ... lines 39 - 48
</div>
</body>
</html>

Refresh, inspect element, then go to network tools, XHR... and clear the filter. When I refresh, we immediately see an AJAX request made for the voyages page! Because of this, when we click this link, watch: it's going to be instant. Boom!

Use this only when you're quite sure what the next page will be. We don't want to trigger a bunch of unnecessary traffic to your site that won't be used.

Oh, and see these JavaScript errors? These come from Symfony's web debug toolbar and profiler. I'm not sure why... but it doesn't like the preloading. That's something we need to fix, but the preloading itself works fine. You can ignore these.

Back in the template, remove the data-turbo-preload... because we don't really know what page the user will click to next.

Today was great. With one library, we eliminated all full page reloads. What could be next? Tomorrow we'll talk about Turbo Frames: a way for us to create Ajax-loading "portions" of our page, without writing a single line of JavaScript.