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<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <type name="MagentoCheckoutBlockCheckoutLayoutProcessor">
        <plugin disabled="false" name="talliance_layout_checkout" sortOrder="11" type="TallianceSwyftShippingMethodPluginMagentoLayoutModelCheckoutLayoutProcessorPlugin"/>
    </type>
</config>

public function afterProcess(LayoutProcessor $layoutProcessor, array $jsLayout)
{
    $jsLayout['components']['checkout']['children']['steps']['children']['shipping-step']['children']
    ['shippingAddress']['children']['shipping-address-fieldset']['children']['city'] = [
        'component' => 'Magento_Ui/js/form/element/select',
        'config' => [
            'customScope' => 'shippingAddress',
            'template' => 'ui/form/field',
            'elementTmpl' => 'ui/form/element/select',
            'id' => 'city'
        ],
        'dataScope' => 'shippingAddress.city',
        'label' => 'City',
        'provider' => 'checkoutProvider',
        'visible' => true,
        'validation' => [ 'required-entry' => true ],
        'sortOrder' => 300,
        'id' => 'city',
        'options' => $this->_cities->toOptionArray(),
    ];
    return $jsLayout;
}

<page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_configuration.xsd">
<body>
    <referenceBlock name="checkout.root">
        <arguments>
            <argument name="jsLayout" xsi:type="array">
                <item name="components" xsi:type="array">
                    <item name="checkout" xsi:type="array">
                        <item name="children" xsi:type="array">
                            <item name="steps" xsi:type="array">
                                <item name="children" xsi:type="array">
                                    <item name="shipping-step" xsi:type="array">
                                        <item name="children" xsi:type="array">
                                            <item name="step-config" xsi:type="array">
                                                <item name="children" xsi:type="array">
                                                    <item name="shipping-rates-validation" xsi:type="array">
                                                        <item name="children" xsi:type="array">
                                                            <item name="swyft-rates-validation" xsi:type="array">
                                                                <item name="component" xsi:type="string">Talliance_SwyftShippingMethod/js/view/shipping-rates-validation/swyft</item>
                                                            </item>
                                                        </item>
                                                    </item>
                                                </item>
                                            </item>
                                        </item>
                                    </item>
                                </item>
                            </item>
                        </item>
                    </item>
                </item>
            </argument>
        </arguments>
    </referenceBlock>
</body>
</page>

define(
    [],
    function () {
        'use strict';
        return {
            getRules: function() {
                return {
                    'city': {
                        'required': true
                    }
                };
            }
        };
    }
);

define(
[
    'jquery',
    'mageUtils',
    '../shipping-rates-validation-rules/swyft',
    'mage/translate'
],
function ($, utils, validationRules, $t) {
    'use strict';
    return {
        validationErrors: [],
        validate: function(address) {
            var self = this;

            this.validationErrors = [];
            $.each(validationRules.getRules(), function (field, rule) {
                var message;

                if (rule.required && utils.isEmpty(address[field])) {
                    message = $t('Field ') + field + $t(' is required.');
                    self.validationErrors.push(message);
                }
            });
            return !this.validationErrors.length;
        }
    };
}
);

define(
[
    'uiComponent',
    'Magento_Checkout/js/model/shipping-rates-validator',
    'Magento_Checkout/js/model/shipping-rates-validation-rules',
    '../../model/shipping-rates-validator/swyft',
    '../../model/shipping-rates-validation-rules/swyft'
],
function (
    Component,
    defaultShippingRatesValidator,
    defaultShippingRatesValidationRules,
    swyftShippingRatesValidator,
    swyftShippingRatesValidationRules
) {
    'use strict';
    defaultShippingRatesValidator.registerValidator('swyft', swyftShippingRatesValidator);
    defaultShippingRatesValidationRules.registerRules('swyft', swyftShippingRatesValidationRules);
    return Component;
});

public function collectRates(RateRequest $request)
{
    if (!$this->getConfigFlag('active')) {
        return false;
    }

   // $data = json_decode(file_get_contents('php://input'), true);
   // $city = $data['address']['shippingAddress']['city'];
   // $this->_logger->log(100, print_r($city,true));

    $rate = $this->getShippingRates();
    $this->_logger->log(100, print_r('rate cost: '.$rate,true));


    if (!$rate) {
        return false;
    }
    $result = $this->_rateFactory->create();
    $method = $this->_rateMethodFactory->create();
    $method->setCarrier($this->_code);
    $method->setCarrierTitle($this->getConfigData('title'));
    $method->setMethod($this->_code);
    $method->setMethodTitle($this->getConfigData('name'));
    $method->setCost($rate);
    $method->setPrice($rate);
    $result->append($method);
    return $result;
}