Symfony Workflow Component - Introductory Lightning Talk
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The symfony workflow component provides a mechanism for defining a life cycle or process which your objects move through, and checking if an object can move to a certain state, and updating the state of the object. This lightning talk introduces the component and how we can use it.
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Symfony Workflow Component - Introductory Lightning Talk
- 1. SYMFONY WORKFLOW COMPONENT @MICHAELPEACOCK, PHPNE, MARCH 2018
- 2. @MICHAELPEACOCK • Consultant CTO • Working with early stage SaaS businesses to build products and teams • Part of the PHPNE Team • Occasional speaker and author
- 3. WORKFLOW COMPONENT A mechanism for defining a life cycle or process which your objects move through, and checking if an object can move to a certain state, and updating the state of the object.
- 4. DEFINITIONS Term Meaning Place State / status / location of your object in the workflow Transition The action from moving from one place to another Definition A set of places and transitions Marking Store Mechanism for getting and setting the place on your object Registry Stores multiple workflows
- 10. PERSISTING STATE • SingleStateMarkingStore • MultipleStateMarkingStore • Implement MarkingStoreInterface
- 13. WORKFLOW
- 14. CHECKING AN OBJECT CAN TRANSITION
- 16. REGISTRY Registry lets you store a number of workflows, and retrieve the appropriate one for a given object
- 18. WORKFLOWS AS A STATE MACHINE • Ensure an object can only be in one place at one time • Introduce cyclic paths e.g. “unpublish”
- 19. EVENT LISTENING SymfonyComponentEventDispatcherEventDispatcherInterface Pass it to the workflow Actions trigger three events, one for every workflow, one for the specific workflow and one for the workflow and transition For instance, when an object has completed a transition, the following events are raised: • workflow.completed • workflow.[workflow name].completed • workflow.[workflow name].completed.[transition name]
- 20. EVENTS workflow.guard Validate to see if the transition is allowed workflow.leave Object is leaving a place workflow.transition Object going through a specific transition workflow.enter Object is about to enter a new place workflow.entered Object has entered new place, and marking updated workflow.completed Object has completed transition workflow.announce Triggered for transitions which are now available to the object
- 21. GUARDING
- 22. QUESTIONS?
Editor's Notes
- A mechanism for defining a life cycle or process which your objects move through, and checking if an object can move to a certain state, and updating the state of the object. For example, if you have a blog, you might define a publishing workflow, if it’s a news website, you could even include editorial checks as part of your workflow.
- Place = status Transition = Moving from one place to another. Definition = Set of places and transitions Marking store = setting and getting the place on your object Registry = stores multiple workflows
- Install via composer.
- Lets use an example of a site which lets uses upload videos, as this is something I’ve started dabbling with for PHPNE videos.
- Firstly, I’m going to create a laravel migration: statuses and videos. Different statuses New (user has created a video record, but not yet uploaded) Uploading. Uploaded. Transcoding. Transcoded. Draft. Published. Video entity has a status.
- Simple models - video and statuses
- Transitions: Name, starting state, subsequent state. Definition is a set of places and transitions, so we tell it all the possible states for a video (ideally, dynamic from our DB), and the transitions. Transitions have a name, a starting place and a subsequent place. They show which places can transition to which other places.
- Persisting state: SingleStateMarkingStore MultipleStateMarkingStore – objects which can be in multiple states Implement MarkingStoreInterface
- Marking store interface. Marking is a wrapper around the place name.
- Example marker when you have a related status table.
- Once we have definitions and a marking store, we pass them along to our workflow.
- We can then check to see if an object is permitted to transition to a particular place, with the can method.
- Apply will transition an object.
- Registry.
- Sample registry.
- In order to use workflows as a state machine, you need to ensure an object can only be in one place at a time (so no multi place), and introduce cyclic paths which tend to exist in state machines but not in workflows. E.g. from published you might have ‘unpublish’
- Event listening. Key actions trigger three different events, which allows you to listen for all workflow tasks, all tasks on a specific workflow and all actions related to a specific workflows transition.
- Different events
- Guarding. Use the event listener, listen for the guard events, and set the event to be blocked.
- Questions.