How to add a custom shipping method rule?

Shipping method rules are used to show shipping methods if certain criteria are fulfilled.

Say you have a requirement for one of your shipping methods that the volume of the shipment may not exceed 1 cubic meter (i.e. 1 m x 1 m 1 m). To model this requirement you can use a shipping method rule.

Create a new shipping method rule

The new rule needs a RuleChecker class:

<?php

namespace App\Shipping\Checker\Rule;

use Sylius\Component\Shipping\Checker\Rule\RuleCheckerInterface;
use Sylius\Component\Shipping\Model\ShippingSubjectInterface;

final class TotalVolumeLessThanOrEqualRuleChecker implements RuleCheckerInterface
{
    public const TYPE = 'total_volume_less_than_or_equal';

    public function isEligible(ShippingSubjectInterface $shippingSubject, array $configuration): bool
    {
        return $shippingSubject->getShippingVolume() <= $configuration['volume'];
    }
}

Prepare a configuration form type for your new rule

To be able to configure a shipping method with your new rule you will need a form type for the admin panel.

Create the configuration form type class:

<?php

namespace App\Form\Type\Rule;

use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\Extension\Core\Type\NumberType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\Validator\Constraints\GreaterThan;
use Symfony\Component\Validator\Constraints\NotBlank;
use Symfony\Component\Validator\Constraints\Type;

class TotalVolumeLessThanOrEqualConfigurationType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options): void
    {
        $builder->add('volume', NumberType::class, [
            'label' => 'app.form.total_volume_less_than_or_equal_configuration.volume',
            'constraints' => [
                new NotBlank(['groups' => ['sylius']]),
                new Type(['type' => 'numeric', 'groups' => ['sylius']]),
                new GreaterThan(['value' => 0, 'groups' => ['sylius']])
            ],
        ]);
    }

    public function getBlockPrefix()
    {
        return 'app_shipping_method_rule_total_volume_less_than_or_equal_configuration';
    }
}

Register the new rule checker as a service in the config/services.yaml:

# config/services.yml
app.shipping_method_rule_checker.total_volume_less_than_or_equal:
    class: App\Shipping\Checker\Rule\TotalVolumeLessThanOrEqualRuleChecker
    tags:
        - { name: sylius.shipping_method_rule_checker, type: total_volume_less_than_or_equal, form_type: App\Form\Type\Rule\TotalVolumeLessThanOrEqualConfigurationType, label: app.form.shipping_method_rule.total_volume_less_than_or_equal }

That’s all. You will now be able to choose the new rule while creating a new shipping method.