Creating an Entity Class

Yo guys! Time to level-up our project in a big way. I mean, big. This series is all about an incredible library called Dog-trine. Wait, that's not right - it's Doctrine. But anyways, Doctrine is kinda like a dog: a dog fetches a bone, Doctrine fetches data from the database. But Doctrine does not pee in the house. That's part of what makes it awesome.

But back up: is Doctrine part of Symfony? Nope. Symfony doesn't care how or if you talk to a database at all. You could use a direct PDO connection, use Doctrine, or do something else entirely. As usual, you're in control.

If you want to code along - which you should - then download the code from the screencast page and move into the directory called start. I already have the start code downloaded, so I'll go straight to opening up a new terminal and starting the built-in sever with:

./bin/console server:run

Perfect!

Doctrine is an ORM

Doctrine is an ORM: object relational mapper. In short, that means that every table - like genus - will have a corresponding PHP class that we will create. When you query the genus table, Doctrine will give you a Genus object. Every property in the class maps to a column in the table. Keep this simple idea in mind as we go along: this mapping between a table and a PHP class is Doctrine's main goal.

Oh, and before we hop in, I want you to remember something very important: all the tools in Symfony are optional, including Doctrine. If Doctrine - or any tool - does more harm than good while solving a problem, skip it and do something simpler. Tools are meant to serve you, not the other way around.

Your First Entity Class

Our sweet app displays information about different ocean-living genuses... but so far, all that info is hardcoded. That's so sad.

Instead, let's create a genus table in the database and load all of this dynamically from there. How do you create a database table with Doctrine? You don't! Your job is to create a class, then Doctrine will create the table based on that class. It's pretty sweet. Oh, and the whole setup is going to take about 2 minutes and 25 lines of code. Watch.

Create an Entity directory in AppBundle and then create a normal class inside called Genus:

You're going to hear this word - entity - a lot with Doctrine. Entity - it sounds like an alien parasite. Fortunately, it's less scary than that: an entity is just a class that Doctrine will map to a database table.

Configuration with... Annotations!

To do that - Doctrine needs to know two things: what the table should be called and what columns it needs. To help it out, we're going to use... drumroll... annotations! Remember, whenever you use an annotation, you need a use statement for it. This will look weird, but add a use for a Column class and let it auto-complete from Doctrine\ORM\Mapping. Remove the Column part and add as ORM:

Every entity class will have that same use statement. Next, put your cursor inside the class and open up the "Code"->"Generate" menu - cmd+N on a Mac. Ooh, one of the options is ORM Class. Click that... and boom! It adds two annotations - @ORM\Entity and @ORM\Table above the class:

Doctrine now knows this class should map to a table called genus.

Configuring the Columns

But that table won't have any columns yet. Lame. Add two properties to get us rolling: id and name. To tell Doctrine that these should map to columns, open up the "Code"->"Generate" menu again - or cmd+N. This time, select ORM Annotation and highlight both properties. And, boom again!

Now we have annotations above each property. The id columns is special - it will almost always look exactly like this: it basically says that id is the primary key.

After that, you'll have whatever other columns you need. Hey, look at the type option that's set to string. That's a Doctrine "type", and it will map to a varchar in MySQL. There are other Doctrine types for strings, floats and text - we'll talk about those soon!

And with just 25 lines of code, we're done! In a second, we'll ask Doctrine to create the genus table for us and we'll be ready to start saving stuff. Well, let's get to it!