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It's time to talk about the most
fundamental part of Symfony: services!

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Honestly, Symfony is nothing more than a
bunch of useful objects that work together.

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For example, there's a router object
that matches routes and generates URLs.

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There's a Twig object that renders templates.

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And there's a Logger object that
Symfony is already using internally

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to store things in a var/log/dev.log file.

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Actually, everything in Symfony
- I mean everything -

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is done by one of these useful objects.

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And these useful objects have
a special name: services.

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But don't get too excited
about that word - service.

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It's a special word for a really simple
idea: a service is any object that does work,

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like generating URLs, sending emails
or saving things to a database.

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Symfony comes with a huge number of services,

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and I want you to think of
services as your tools.

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Like, if I gave you the logger service, or
object, then you could use it to log messages.

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If I gave you a mailer service,
you could send some emails!

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Tools! The entire second half
of Symfony is all about learning

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where to find these services
and how to use them.

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Every time you learn about a
new service, you get a new tool,

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and become just a little bit more dangerous!

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Let's check out the logging system.

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Find your terminal and run: tail -f
var/log/dev.log I'll clear the screen.

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Now, refresh the page, and move back.

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Awesome! This proves that Symfony
has some sort of logging system.

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And since everything is done by a
service, there must be a logger object.

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So here's the question: how
can we get the logger service

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so that we can log our own messages?

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Here's the answer: inside the controller,
on the method, add an additional argument.

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Give it a LoggerInterface type hint
- hit tab to auto-complete that

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and call it whatever you
want, how about $logger.

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Remember: when you autocomplete, PhpStorm
adds the use statement to the top for you.

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Now, we can use one of its methods:
$logger->info('Article is being hearted').

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Before we talk about this, let's try it!

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Find your browser and click the heart.

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That hit the AJAX endpoint.

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Go back to the terminal.

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Yes! There it is at the bottom.

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Hit Ctrl+C to exit tail.

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Ok cool! But...

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how the heck did that work?

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Here's the deal: before Symfony executes
our controller, it looks at each argument.

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For simple arguments like $slug, it passes
us the wildcard value from the router.

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But for $logger, it looks at
the type-hint and realizes

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that we want Symfony to pass
us the logger object.

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Oh, and the order of the
arguments does not matter.

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This is a very powerful idea called
autowiring: if you need a service object,

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you just need to know the
correct type-hint to use!

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So... how the heck did I
know to use LoggerInterface?

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Well, of course, if you look at the official
Symfony docs about the logger, it'll tell you.

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But, there's a cooler way.

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Go to your terminal and run: .

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/bin/console debug:autowiring Boom!

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This is a full list of all of the
type-hints that you can use to get a service.

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Notice that most of them say that
they are an alias to something.

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Don't worry about that too much: like routes,

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each service has an internal
name you can use to reference it.

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We'll learn more about that later.

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Oh, and whenever you install a new package,
you'll get more and more services in this list.

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More tools!

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And check this out!

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If you want to get the Twig service, you
can use either of these two type-hints.

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And remember how I said that everything
in Symfony is done by a service?

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Well, when we call $this->render() in
a controller, that's just a shortcut

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to fetch the Twig service
and call a method on it.

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In fact, let's pretend that the
$this->render() shortcut does not exist.

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How could we render a template?

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No problem: we just need the Twig service.

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Add a second argument with
an Environment type-hint,

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because that's the class name
we saw in debug:autowiring.

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Call the arg $twigEnvironment.

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Next, change the return statement to
be $html = $twigEnvironment->render().

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The method we want to call on the
Twig object is coincidentally the same

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as the controller shortcut.

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Then at the bottom, return
new Response() and pass $html.

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Ok, this is way more work than before...

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and I would not do this in a real project.

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But, I wanted to prove a point: when you
use the $this->render() shortcut method

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on the controller, all it really does
is call render() on the Twig service

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and then wrap it inside a
Response object for you.

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Try it! Go back and refresh the page.

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It works exactly like before!

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Of course we will use shortcut methods,
because they make our life way more awesome.

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I'll change my code back
to look like it did before.

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But the point is this: everything
is done by a service.

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If you learn to master services, you can
do anything from anywhere in Symfony.

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There's a lot more to say about the topic of
services, and so many other parts of Symfony:

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configuration, Doctrine & the database,
forms, Security and APIs, to just name a few.

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The Space Bar is far from being the galactic
information source that we know it will be!

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But, congrats!

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You just spent an hour getting
an awesome foundation in Symfony.

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You will not regret your hard work: you're
on your way to building great things and,

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as always, becoming a better
and better developer.

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Alright guys, seeya next time!