The Workflow ComponentEdit this page
The Workflow component provides tools for managing a workflow or finite state machine.
$ composer require symfony/workflow
If you install this component outside of a Symfony application, you must
vendor/autoload.php file in your code to enable the class
autoloading mechanism provided by Composer. Read
this article for more details.
The workflow component gives you an object oriented way to define a process or a life cycle that your object goes through. Each step or stage in the process is called a place. You do also define transitions that describe the action to get from one place to another.
A set of places and transitions creates a definition. A workflow needs
Definition and a way to write the states to the objects (i.e. an
instance of a MarkingStoreInterface).
Consider the following example for a blog post. A post can have one of a number
of predefined statuses (
published). In a workflow,
these statuses are called places. You can define the workflow like this:
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use Symfony\Component\Workflow\DefinitionBuilder; use Symfony\Component\Workflow\MarkingStore\MethodMarkingStore; use Symfony\Component\Workflow\Transition; use Symfony\Component\Workflow\Workflow; $definitionBuilder = new DefinitionBuilder(); $definition = $definitionBuilder->addPlaces(['draft', 'reviewed', 'rejected', 'published']) // Transitions are defined with a unique name, an origin place and a destination place ->addTransition(new Transition('to_review', 'draft', 'reviewed')) ->addTransition(new Transition('publish', 'reviewed', 'published')) ->addTransition(new Transition('reject', 'reviewed', 'rejected')) ->build() ; $singleState = true; // true if the subject can be in only one state at a given time $property = 'currentState'; // subject property name where the state is stored $marking = new MethodMarkingStore($singleState, $property); $workflow = new Workflow($definition, $marking);
Workflow can now help you to decide what transitions (actions) are allowed
on a blog post depending on what place (state) it is in. This will keep your domain
logic in one place and not spread all over your application.
Here's an example of using the workflow defined above:
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// ... // Consider that $blogPost is in place "draft" by default $blogPost = new BlogPost(); $workflow->can($blogPost, 'publish'); // False $workflow->can($blogPost, 'to_review'); // True $workflow->apply($blogPost, 'to_review'); // $blogPost is now in place "reviewed" $workflow->can($blogPost, 'publish'); // True $workflow->getEnabledTransitions($blogPost); // $blogPost can perform transition "publish" or "reject"
If the property of your object is
null and you want to set it with the
initial_marking from the configuration, you can call the
method to initialize the object property:
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// ... $blogPost = new BlogPost(); // initiate workflow $workflow->getMarking($blogPost);
When you define multiple workflows you may consider using a
which is an object that stores and provides access to different workflows.
A registry will also help you to decide if a workflow supports the object you
are trying to use it with:
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use Acme\Entity\BlogPost; use Acme\Entity\Newsletter; use Symfony\Component\Workflow\Registry; use Symfony\Component\Workflow\SupportStrategy\InstanceOfSupportStrategy; $blogPostWorkflow = ...; $newsletterWorkflow = ...; $registry = new Registry(); $registry->addWorkflow($blogPostWorkflow, new InstanceOfSupportStrategy(BlogPost::class)); $registry->addWorkflow($newsletterWorkflow, new InstanceOfSupportStrategy(Newsletter::class));
You can then use the registry to get the workflow for a specific object:
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$blogPost = new BlogPost(); $workflow = $registry->get($blogPost); // initiate workflow $workflow->getMarking($blogPost);
Beware that injecting the
Registry into your services is not
recommended. Indeed, it prevents some optimization like lazy-loading
from working and could be a performance hog. Instead, you should always
inject the workflow you need.