Workflow

Using the Workflow component inside a Symfony application requires to know first some basic theory and concepts about workflows and state machines. Read this article </workflow/workflow-and-state-machine> for a quick overview.

Installation

In applications using Symfony Flex <symfony-flex>, run this command to install the workflow feature before using it:

$ composer require symfony/workflow

Configuration

To see all configuration options, if you are using the component inside a Symfony project run this command:

$ php bin/console config:dump-reference framework workflows

Creating a Workflow

A workflow is a process or a lifecycle that your objects go through. Each step or stage in the process is called a place. You do also define transitions to that describes the action to get from one place to another.

A set of places and transitions creates a definition. A workflow needs a Definition and a way to write the states to the objects (i.e. an instance of a Symfony\\Component\\Workflow\\MarkingStore\\MarkingStoreInterface.)

Consider the following example for a blog post. A post can have these places: draft, reviewed, rejected, published. You can define the workflow like this:

# config/packages/workflow.yaml
framework:
    workflows:
        blog_publishing:
            type: 'workflow' # or 'state_machine'
            audit_trail:
                enabled: true
            marking_store:
                type: 'method'
                property: 'currentPlace'
            supports:
                - App\Entity\BlogPost
            initial_marking: draft
            places:
                - draft
                - reviewed
                - rejected
                - published
            transitions:
                to_review:
                    from: draft
                    to:   reviewed
                publish:
                    from: reviewed
                    to:   published
                reject:
                    from: reviewed
                    to:   rejected

<!-- config/packages/workflow.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:framework="http://symfony.com/schema/dic/symfony"
    xsi:schemaLocation="http://symfony.com/schema/dic/services
    https://symfony.com/schema/dic/services/services-1.0.xsd
    http://symfony.com/schema/dic/symfony
    https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">

    <framework:config>
        <!-- or type="state_machine" -->
        <framework:workflow name="blog_publishing" type="workflow">
            <framework:audit-trail enabled="true"/>
            <framework:marking-store type="single_state">
                <framework:argument>currentPlace</framework:argument>
            </framework:marking-store>
            <framework:support>App\Entity\BlogPost</framework:support>
            <framework:initial-marking>draft</framework:initial-marking>
            <framework:place>draft</framework:place>
            <framework:place>reviewed</framework:place>
            <framework:place>rejected</framework:place>
            <framework:place>published</framework:place>
            <framework:transition name="to_review">
                <framework:from>draft</framework:from>
                <framework:to>reviewed</framework:to>
            </framework:transition>
            <framework:transition name="publish">
                <framework:from>reviewed</framework:from>
                <framework:to>published</framework:to>
            </framework:transition>
            <framework:transition name="reject">
                <framework:from>reviewed</framework:from>
                <framework:to>rejected</framework:to>
            </framework:transition>
        </framework:workflow>
    </framework:config>
</container>

// config/packages/workflow.php
use App\Entity\BlogPost;

$container->loadFromExtension('framework', [
    'workflows' => [
        'blog_publishing' => [
            'type' => 'workflow', // or 'state_machine'
            'audit_trail' => [
                'enabled' => true
            ],
            'marking_store' => [
                'type' => 'method',
                'property' => 'currentPlace',
            ],
            'supports' => [BlogPost::class],
            'initial_marking' => 'draft',
            'places' => [
                'draft',
                'reviewed',
                'rejected',
                'published',
            ],
            'transitions' => [
                'to_review' => [
                    'from' => 'draft',
                    'to' => 'reviewed',
                ],
                'publish' => [
                    'from' => 'reviewed',
                    'to' => 'published',
                ],
                'reject' => [
                    'from' => 'reviewed',
                    'to' => 'rejected',
                ],
            ],
        ],
    ],
]);

Tip

If you are creating your first workflows, consider using the workflow:dump command to debug the workflow contents </workflow/dumping-workflows>.

The configured property will be used via it's implemented getter/setter methods by the marking store:

class BlogPost
{
    // the configured property must be declared
    private $currentPlace;
    private $title;
    private $content;

    // getter/setter methods must exist for property access by the marking store
    public function getCurrentPlace()
    {
        return $this->currentPlace;
    }

    public function setCurrentPlace($currentPlace, $context = [])
    {
        $this->currentPlace = $currentPlace;
    }
}

Note

The marking store type could be "multiple_state" or "single_state". A single state marking store does not support a model being on multiple places at the same time. This means a "workflow" must use a "multiple_state" marking store and a "state_machine" must use a "single_state" marking store. Symfony configures the marking store according to the "type" by default, so it's preferable to not configure it.

A single state marking store uses a string to store the data. A multiple state marking store uses an array to store the data.

Tip

The marking_store.type (the default value depends on the type value) and property (default value ['marking']) attributes of the marking_store option are optional. If omitted, their default values will be used. It's highly recommenced to use the default value.

Tip

Setting the audit_trail.enabled option to true makes the application generate detailed log messages for the workflow activity.

With this workflow named blog_publishing, you can get help to decide what actions are allowed on a blog post:

use App\Entity\BlogPost;
use Symfony\Component\Workflow\Exception\LogicException;

$post = new BlogPost();

$workflow = $this->container->get('workflow.blog_publishing');
$workflow->can($post, 'publish'); // False
$workflow->can($post, 'to_review'); // True

// Update the currentState on the post
try {
    $workflow->apply($post, 'to_review');
} catch (LogicException $exception) {
    // ...
}

// See all the available transitions for the post in the current state
$transitions = $workflow->getEnabledTransitions($post);

Accessing the Workflow in a Class

To access workflow inside a class, use dependency injection and inject the registry in the constructor:

use Symfony\Component\Workflow\Registry;

class MyClass
{

    private $workflowRegistry;

    public function __construct(Registry $workflowRegistry)
    {
        $this->workflowRegistry = $workflowRegistry;
    }

    public function toReview(BlogPost $post)
    {
        $workflow = $this->workflowRegistry->get($post);

        // Update the currentState on the post
        try {
            $workflow->apply($post, 'to_review');
        } catch (LogicException $exception) {
            // ...
        }
        // ...
    }
}

Using Events

To make your workflows more flexible, you can construct the Workflow object with an EventDispatcher. You can now create event listeners to block transitions (i.e. depending on the data in the blog post) and do additional actions when a workflow operation happened (e.g. sending announcements).

Each step has three events that are fired in order:

An event for every workflow;
An event for the workflow concerned;
An event for the workflow concerned with the specific transition or place name.

When a state transition is initiated, the events are dispatched in the following order:

workflow.guard

Validate whether the transition is blocked or not (see guard events <workflow-usage-guard-events> and blocking transitions <workflow-blocking-transitions>).