Score:4

Drupal

How do I use \Drupal methods in a class?

lilHar

4/17/24, 11:05 PM

I was out of Drupal for a few years, and PHP a couple years, due to having several years of jobs that didn't use Drupal between two that did. And I'm noticing a lot of functions that were reliable are now gone.

The particular case I am currently looking at is variable_get() occurrences replaced by \Drupal::state()->get().

However, I tried using it, and it's far from a drop-in replacement. In a class in a module I was working on, I tried changing $lm = variable_get('user_import_line_max'); to $line_max = \Drupal::state()->get('user_import_line_max'); but this complained that it can't be used inside a class (despite the fact the function could).

How do I use \Drupal methods in a class?

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cilefen

4/18/24, 12:36 AM

Welcome to Drupal Answers! This site is set up for answering one question at a time.

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cilefen

4/18/24, 12:39 AM

What does "this complained that it can't be used inside a class" mean, technically? Are you talking about the documentation which suggests it is an unsustainable practice, or, some kind of an error message?

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lilHar

4/18/24, 1:56 PM

@cilefen I've already started refactoring my code so I don't get the error anymore, but it was specifically an error when I first tried it, along the lines of "\Drupal::state()->get() cannot be used inside of a class".

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Score:8

Drupal

cilefen

4/18/24, 12:51 AM

\Drupal::state() is a static helper function intended for use in procedural code. It returns the singleton "State" object (called a "service") from the service container. \Drupal::state()->get() is a chained method call that then calls the get method on the state service.

In object-oriented code the advice is to use dependency injection patterns, the most common type of which is constructor injection, to obtain service container objects. A strong argument for using dependency injection is that it facilitates unit testing your classes. The Drupal API documentation I linked to in the above paragraph explains using the service container in some detail.

As a sample you could look at core's DbUpdateController.php. There you can see how the State service is first injected:

And how it later is used inside the controller:

+ 1

4uk4

4/18/24, 10:02 AM

The added sample is a more complex DI pattern using the factory method create(). See https://en.wikipedia.org/wiki/Factory_method_pattern. In Drupal this is only necessary for controllers or plugins, which are not registered as service in the container.

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Score:4

Drupal

Jaypan

4/18/24, 1:55 PM

To add to Cliefen's very good answer, you can view the documentation for the \Drupal class here: https://api.drupal.org/api/drupal/core%21lib%21Drupal.php/class/Drupal/10

It provides a list of all functions that can be called statically off the class.

+ 4

lilHar

4/18/24, 1:58 PM

One thing I'm still trying to figure out is what that leading slash does in \Drupal, as I haven't really seen that before. Is it literally just part of the name, like the dollar sign in JQuery (which I loath due to it interfering with me writing PHP code) or is it actually doing something?

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4uk4

4/18/24, 2:42 PM

This is about namespaces. See https://www.php.net/manual/en/language.namespaces.rules.php. `\Drupal` is a fully-qualified class name while `Drupal` is not. The latter works only if you add `use Drupal;` to a class or in procedural code.

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Jaypan

4/18/24, 3:16 PM

The back slash at the start indicates that the class is in the global namespace. So `\Drupal` is in the global namespace. An example module for example could declare it's own class named `Drupal` in a separate namespace, such as `\Drupal\example\Drupal`, and these would not conflict, as they are in different namespaces.

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lilHar

4/19/24, 2:56 PM

Ah, so that's why I never came across it before, as I tend to avoid coding with globals and Drupal didn't use to use it. Thanks for the clarification!

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