Using the Workflow component for e-commerce

Open Conﬁrmed
Assigned
To
Picker
Picked
Up
Delivered
Cancelled
Aborted
Cancelled
By
System
Cancel Order
For technical Reasons
Cancel
Abort
Checkout
Assign to
picker
Pick Up
Deliver
Cancel
Cancel Cancel

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Open Open
UpdateItem

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State machines
make business
logic explicit

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Open Conﬁrmed
Assigned
To
Picker
Picked
Up
Delivered
Cancelled
Aborted
Cancelled
By
System
Cancel Order
Cancel
Abort
Checkout
Assign to
picker
Pick Up
Deliver
Cancel
Cancel Cancel

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A workflow does not contain all logic

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The Workﬂow
Component

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composer require
symfony/workflow

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Our Workflow

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Open Conﬁrmed
Assigned
To
Picker
Picked
Up
Delivered
Cancelled
Aborted
Cancelled
By
System
Cancel Order
Cancel
Abort
Checkout
Assign to
picker
Pick Up
Deliver
Cancel
Cancel Cancel

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framework:

workﬂows:

order:

type: state_machine

marking_store:

type: 'single_state'

arguments:

- 'state'

supports:

- AppBundle\Entity\Order

places:

- open

- conﬁrmed

- assigned-to-delivery-person

- picked-up

- delivered

- aborted

- cancelled

transitions:

updateItem:

from: open

to: open

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framework:

workﬂows:

order:

type: state_machine

marking_store:


arguments:

- 'state'

supports:


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framework:

workﬂows:

order:

type: state_machine

marking_store:


arguments:

- 'state'

supports:


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framework:

workﬂows:

order:

type: state_machine
marking_store:


arguments:

- 'state'

supports:


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framework:

workﬂows:

order:

type: state_machine

marking_store:
arguments:
- 'state'
supports:


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framework:

workﬂows:

order:

type: state_machine

marking_store:


arguments:

- 'state'

supports:

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places:
- open

- conﬁrmed

- assigned-to-picker

- picked-up

- delivered

- aborted

- cancelled

- cancelled-by-system

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transitions:
updateItem:

from: open

to: open

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The Model

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public const STATE_OPEN = 'open';
public const STATE_CONFIRMED = 'confirmed';
public const STATE_ASSIGNED_TO_PICKER = 'assigned-to-picker';
public const STATE_PICKED_UP = 'picked-up';
public const STATE_DELIVERED = 'delivered';
public const STATE_ABORTED_BY_CUSTOMER = 'aborted';
public const STATE_CANCELLED_BY_SUPPORT = 'cancelled';
public const STATE_CANCELLED_BY_SYSTEM = 'cancelled-by-system';

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public const STATES = [
self::STATE_OPEN,
self::STATE_CONFIRMED,
self::STATE_ASSIGNED_TO_PICKER,
self::STATE_PICKED_UP,
self::STATE_DELIVERED,
self::STATE_ABORTED_BY_CUSTOMER,
self::STATE_CANCELLED_BY_SUPPORT,
self::STATE_CANCELLED_BY_SYSTEM,
];

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public const TRANSITION_UPDATE_ITEM = 'updateItem';

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/**
* @var string
*/
private $state = self::STATE_OPEN;

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Events

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Solves Tight Coupling

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EventDispatcher

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composer require
symfony/event-dispatcher

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The Listener

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class OrderWorkflowListener implements EventSubscriberInterface
{ 
…
}

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/**
* @return array Hashmap of Symfony events this handler cares about
*/
public static function getSubscribedEvents()
{
return [
// Guard events (Validate whether the transition is allowed at all)
'workflow.order.guard' => 'guardGeneralOrderWorkflow',
sprintf('workflow.order.guard.%s', Order::TRANSITION_CHANGE_REGION) => 'guardChangeRegion',
sprintf('workflow.order.guard.%s', Order::TRANSITION_CONFIRM_ORDER) => 'guardConfirmOrder',
sprintf('workflow.order.guard.%s', Order::TRANSITION_ASSIGN_PICKER) => 'guardAssignPicker',
sprintf('workflow.order.guard.%s', Order::TRANSITION_ASSIGN_CUSTOMER) => 'guardAssignCustomer',
// Enter events (The object is about to enter a new place)
sprintf('workflow.order.enter.%s', Order::STATE_CONFIRMED) => 'enterConfirmed',
sprintf('workflow.order.enter.%s', Order::STATE_DELIVERED) => 'enterDelivered',
// Entered events (The object entered a new place)
sprintf('workflow.order.entered.%s', Order::STATE_PICKED_UP) => 'enteredPickedUp',
// The object has completed this transition.
'workflow.order.completed' => 'onCompleted',
];
}

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/**
*/
{
return [
];
}

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/**
*/
{
return [
];
}

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/**
*/
{
return [
];
}

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/**
*/
{
return [
];
}

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Workﬂow
component does so
much for us

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Order API
Challenges Solved

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Keeping orders/prices
up to date

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public function onCompleted(Event $event): void
{
$transition = $event->getTransition();
$fromState = $transition->getFroms()[0];
/** @var Order $order */
$order = $event->getSubject();
// If an order is already in delivered state, all calculations are done, and should stay as
they are.
if (Order::STATE_DELIVERED !== $fromState) {
$this->orderModifier->updateTotals($order);
}
$this->orderStateHistoryRepository->storeOrderStateTransition($order, $transition);
$this->orderEventService->eventHappened($transition->getName(), $order->getId(), $fromState);
}

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{
they are.
}
}

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}

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Making our
consumers love us 
(Good error messages and
documentation)

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Handling cancellation of
an order

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Handling a large amount
of SMS and Push
notifications

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{
they are.
}
}

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{
they are.
}
}

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public function eventHappened(string $type, string $orderId, ?string $previousState)
{
foreach ($this->handlers as $handler) {
if ($handler->canHandle($type)) {
$this->orderEventProducer->publish(
$type,
$orderId,
$previousState,
$handler->getPriority()
);
return;
}
}
}

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public function eventHappened(string $type, string $orderId, ?string $previousState)
{
foreach ($this->handlers as $handler) {
if ($handler->canHandle($type)) {
$this->orderEventProducer->publish(
$type,
$orderId,
$previousState,
$handler->getPriority()
);
return;
}
}
}

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class SmsNotificationHandler implements OrderEventHandler
{
private const TRANSITION_STATE_MAP = [
Order::TRANSITION_ASSIGN_PICKER => Order::STATE_ASSIGNED_TO_PICKER,
Order::TRANSITION_TIMEOUT_FINDING_PICKER => Order::STATE_ABORTED_BY_CUSTOMER,
Order::TRANSITION_PICKER_CONFIRMS_PURCHASE => Order::STATE_PICKED_UP,
Order::TRANSITION_CONFIRM_DELIVERY => Order::STATE_DELIVERED,
Order::TRANSITION_REFERRAL_PICKER_RECEIVES_REWARD => Order::STATE_DELIVERED,
Order::TRANSITION_SEND_ORDER_AVAILABLE_REMINDER => Order::STATE_CONFIRMED,
];

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public function canHandle(string $type): bool
{
return array_key_exists($type, self::TRANSITION_STATE_MAP);
}

Using the Workflow component for e-commerce

Using the Workflow component for e-commerce

Michelle Sanver

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