Persisting to the Database

Now that we have an entity class and corresponding table, we're ready to save some stuff! So... how do we insert rows into the table? Wrong question! We're only going to focus on creating objects and saving them. Doctrine will handle the insert queries for us.

To help do this in the simplest way possible, let's make a fake "new Vinyl Mix" page.

In the src/Controller/ directory, create a new MixController class and make this extend the normal AbstractController. Perfect! Inside, add a public function called new() that will return a Response from HttpFoundation. To make this a page, above, use the #[Route] attribute, hit "tab" to autocomplete that and let's call the URL /mix/new. Finally, to see if this is working, dd('new mix').

In the real world, this page might render a form. Then, when we submit that form, we would take its data, create a VinylMix() object and save it. We'll work on stuff like that in a future tutorial. For now, let's just see if this page works. Head over to /mix/new and... got it!

Ok, let's go create a VinylMix() object! Do that with $mix = new VinylMix()... and then we can start setting data on it! Let's create a mix of one of my absolute favorite artists as a kid. I'll quickly set some other properties... we need to set, at the very least, all of the properties that have required columns in the database. For trackCount, how about some randomness for fun. And, for votes, the same thing... including negative votes... though the Internet would never be so cruel as to downvote any of my mixes that much. Finally, dd($mix).

So far, this has nothing to do with Doctrine. We're just creating an object and setting data onto it. This data is hard-coded, but you can imagine replacing this with whatever the user just submitted via a form. Regardless of where we get the data, when we refresh... we have an object with data on it. Cool!

Services vs Entities

By the way, our entity class, VinylMix, is the first class we've created that is not a service. There are generally two types of classes. First, there are service objects, like TalkToMeCommand or the MixRepository we created in the last tutorial. These objects do work... but they don't hold any data besides maybe some basic config. And we always fetch services from the container, usually via autowiring. We never instantiate them directly.

The second type of classes are data classes like VinylMix. The primary job of these classes is to hold data. They don't usually do any work except maybe some basic data manipulation. And unlike services, we don't fetch these objects from the container. Instead, we create them manually wherever and whenever we need them, like we just did!

Hello Entity Manager!

Anyway, now that we have an object, how can we save it? Well, saving something to the database is work. And so, no surprise, that work is done by a service! Add an argument to the method, type-hinted with EntityManagerInterface. Let's call it $entityManager.

EntityManagerInterface is, by far, the most important service for Doctrine. We're going to use it to save, and indirectly when we query. To save, call $entityManager->persist() and pass it the object that we want to save (in this case, $mix). Then we also need to call $entityManager->flush() with no arguments.

But... wait. Why do we have to call two methods?

Here's the deal. When we call persist(), that doesn't actually save the object or talk to the database at all. It just tells Doctrine:

Hey! I want you to be "aware" of this object, so that later when we call flush(), you'll know to save it.

Most of the time, you'll see these two lines together - persist() and then flush(). The reason it's split into two methods is to help with batch data loading... where you could persist a hundred $mix objects and then flush them to the database all at once, which is more efficient. But most of the time, you'll call persist() and then flush().

Okay, to make this a valid page, let's return new Response() from HttpFoundation and I'll use sprintf to return a message: mix %d is %d tracks of pure 80\'s heaven... and for those two wildcards, pass $mix->getId() and $mix->getTrackCount().

Let's try it! Move over, refresh and... yes! We see "Mix 1". That's so cool! We never actually set the ID (which makes sense). But when we saved, Doctrine grabbed the new ID and put that onto the id property.

If we refresh a few more times, we get mixes 2, 3, 4, 5, and 6. That's super fun. All we had to do is persist and flush the object. Doctrine handles all of the querying stuff for us.

Another way we can prove this is working is by running:

symfony console doctrine:query:sql 'SELECT * FROM vinyl_mix'

This time, we do see the results. Awesome!

Okay, now that we have stuff in the database, how do we query for it? Let's tackle that next.