Configuring our Bundle's Entity

We created the abstract Translation class in our bundle. Now, we need to tell Doctrine about it so we can extend and use it in our app as a real entity.

First, hope over to your terminal and run:

symfony console doctrine:mapping:info

This shows all the entities that Doctrine knows about. The Category, Tag, and Article entities from our app, is all we see right now. This command also shows mapped superclasses, so we need to do some work to get our Translation class to show up here.

You're probably used to using mapping attributes for your Doctrine entities. In bundles, it's a bit different. The official recommendation is to use XML for the mapping. I know, I know, XML is not the most fun thing to work with, but it does provide the most flexibility.

Creating the XML File

Let's get down to business. In your bundle's config directory, create a new directory and subdirectory: doctrine/mapping. To save you the pain of watching me struggle to write the XML, in the tutorial directory, there's a Translation.orm.xml file. Grab that file and move it in into our new doctrine/mapping directory.

Note the .orm.xml suffix. This is important as it tells Doctrine that this is mapping information for the ORM. In the future, if we add support for MongoDB, we'd create a Translation.mongodb.xml file with the appropriate mapping for that.

Understanding the XML File

Open Translation.orm.xml in your editor. Gross... let's unpack this. First, we're declaring a top-level doctrine-mapping element with some XML namespace stuff. Inside, a mapped-superclass element with a name attribute for the full class name of our bundle's Translation class.

Inside this, is our field mappings. The name attribute corresponds to the property name in our Translation class, and the column attribute is the column name we want to use in the database. If omitted, Doctrine will use the property name as the column name. I've snake_cased the objectType and objectId column names to follow common database naming conventions.

The type attribute indicates the Doctrine type for the column. We'll use string for all except for value, which is text. string columns have a maximum length, typically around 200-250 characters, depending on the database platform and configuration. This is fine for most of our fields, but the value column needs to hold more. The text type can hold much larger strings, so it's perfect for our translated values.

Loading the XML Mapping

Just creating the XML file isn't enough though, we need to let Doctrine know about this file. In ObjectTranslationBundle, override the build() method and add the void return type. This parent method call can be removed, as it's empty.

loadExtension() is where we load and configure things for this bundle. build() is called later in the process, after all other bundles have been registered. This allows us to modify the service container after all other bundles have had a chance to register their services. Here, we can tell Doctrine about our bundle's mappings.

We'll do this with a compiler pass, a sort of build hook that has access to the fully built service container. Write $container->addCompilerPass().

Doctrine provides a compiler pass specifically for loading mappings. Write DoctrineOrmMappingsPass and import this class from the Doctrine bundle. Here we can see the static methods to create mappings. Choose createXmlMappingDriver().

The first argument is an array. The keys are the directories where the mapping files are located, and the values are the namespaces that these mapping files represent. We only need one.

For the key, use __DIR__.'/../config/doctrine/mapping' - this is the relative path to our mapping directory. For the value, jump over to the Translation class and copy its namespace SymfonyCasts\ObjectTranslationBundle\Model. Go back to ObjectTranslationBundle and paste it in as the value.

That's it!

Jump over to your terminal and run the doctrine:mapping:info command again:

symfony console doctrine:mapping:info

Sweet! Now we can see our Translation mapped superclass listed.

Next, we'll create the real Translation entity in our app!