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Step 4 - Register the Field Type as a service

Tip

You can find all files used and modified in this step on GitHub.

To complete the implementation, you must register the Field Type with Symfony by creating a service for it.

Services are by default declared by bundles in Resources/config/services.yml.

Using a dedicated file for the Field Type services

In order to be closer to the kernel best practices, you will declare the Field Type services in a custom fieldtypes.yml file.

All you have to do is instruct the bundle to load this file in addition to services.yml. This is done in the extension definition file, DependencyInjection/EzSystemsTweetFieldTypeExtension.php, in the load() method.

Inside this file, find this line:

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$loader->load('services.yml');

This is where the bundle tells Symfony that when parameters are loaded, services.yml should be loaded from Resources/config/ (defined above). Add a new line either before or after this one:

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$loader->load('fieldtypes.yml');

Like most API components, Field Types use the Symfony service tag mechanism.

A service can be assigned one or several tags, with specific parameters. When the dependency injection container is compiled into a PHP file, tags are read by CompilerPass implementations that add extra handling for tagged services. Each service tagged as ezpublish.fieldType is added to a registry using the alias argument as its unique identifier (ezstring, ezxmltext, etc.). Each Field Type must also inherit from the abstract ezpublish.fieldType service. This ensures that the initialization steps shared by all Field Types are executed.

Now you can create a YAML file dedicated to the bundle: Resources/config/fieldtypes.yml

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services:
    ezsystems.tweetbundle.fieldtype.eztweet:
        parent: ezpublish.fieldType
        class: EzSystems\TweetFieldTypeBundle\eZ\Publish\FieldType\Tweet\Type
        tags:
            - {name: ezpublish.fieldType, alias: eztweet}
            - {name: ezpublish.fieldType.nameable, alias: eztweet}
        arguments: ['@ezsystems.tweetbundle.twitter.client']

Namespacing the Field Type with your vendor and bundle name limits the risk of naming conflicts.

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