SilverShop checkout address validation

CheckoutControllerExtension.php

<?php

/**
 * Apply this extension to the checkout page controller, eg:
 *
 * ```
 * CheckoutPage_Controller:
 *   extensions:
 *     - CheckoutControllerExtension
 * ```
 */

class CheckoutControllerExtension extends Extension
{
    public function updateConfirmationComponentConfig($config)
    {
        $config->addComponent(new ValidateAddressCheckoutComponent());
    }
}

shopconfig.yml

---
Name: shop-config
---

CheckoutPage_Controller:
  extensions:
    - CheckoutControllerExtension

ValidateAddressCheckoutComponent.php

<?php

/**
 * Validation component to validate an order contains a valid address
 */
class ValidateAddressCheckoutComponent extends CheckoutComponent
{
    public function getFormFields(Order $order)
    {
        $fields = new FieldList();

        $fields->add(HiddenField::create('_address', $order->getShippingAddress()->ID));
        /** @var ValidationResult $validation */
        $validation = $order->getShippingAddress()->validate();

        if(!$validation->valid()){
            $fields->add(LiteralField::create('_warn_Address',
                '<div class="message warn missing-address">'.$this->MissingAddressMessage().'</div>'
            ));
        }

        return $fields;
    }

    public function getRequiredFields(Order $order)
    {
        return array();
    }

    public function validateData(Order $order, array $data)
    {
        $validation = $order->getShippingAddress()->validate();
        if(!$validation->valid()){
            throw new ValidationException($this->MissingAddressMessage());
        }
        return $validation->valid();
    }

    public function setData(Order $order, array $data)
    {
    }

    public function getData(Order $order)
    {
        return array();
    }

    protected function MissingAddressMessage()
    {
        return _t(
            'Checkout.NO_ADDRESS',
            'No Address given. <a href="{Link}">Please go enter one</a>',
            '',
            array('Link' => Controller::curr()->Link('shippingaddress'))
        );
    }
}