Difference between ContainerInjectionInterface and ContainerFactoryPluginInterface?

mbomb007

2/2/24, 9:29 PM

Both ContainerInjectionInterface and ContainerFactoryPluginInterface provide a create() function and are used for dependency injection.

I would like a clear description of their differences and their use cases, such that it's clear which interface a class should implement.

Which should I use if I only need to use injected services in a class?
Which should I use in a service class that will be injected in other classes and defined in the module.services.yml?

249

1 + 0

dependency-injection

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Drupal

4uk4

2/2/24, 10:05 PM

The first one is typically used for controllers and the second one is for plugins. If you only need to inject services in service classes defined in module.services.yml you need neither of them.

+ 4

mbomb007

2/3/24, 4:16 PM

I just looked at Cron.php and its entry in core.services.yml, and it looks like a good example of how you don't need to implement one to inject services. So basically, you only need `ContainerFactoryPluginInterface` if you intend to inject your class into another class?

Clive

2/3/24, 4:29 PM

No, you only need `ContainerFactoryPluginInterface` if you're creating a plugin. A basic service that can be injected into another class doesn't need to implement _any_ interfaces to get the DI working. The definition in services.yml provides that function. In reality all `ContainerFactoryPluginInterface` does is force the class to have a `create` method, which is provided the container as an argument, so you can instantiate a class with injected services. You already define those services in services.yml for a "normal" service, so no interface is needed

Jaypan

2/3/24, 4:30 PM

Plugins don't by definition call the `create()` method, so there is no dependency injection. If you are creating a plugin that needs dependency injunction, you would declare `ContainerFactoryPluginInterface`.

mbomb007

2/3/24, 5:53 PM

Thanks. After removing a bunch of needless `implements ContainerPluginInterface`, I don't need it anywhere. It's still used for controllers and forms, but in those cases you end up extending `ControllerBase` or `FormBase` and you don't need to add it yourself.

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