I am trying to create custom validation for products in the Magento 2 cart.

I have created a plugin:

<type name="Magento\Checkout\Controller\Index\Index">
    <plugin name="checkQuantityGroups"

With the following code:

public function beforeExecute()
    // Get quote from session

    /** @var Quote $quote */
    $quote = $this->checkoutSession->getQuote();

    // Get items in quote
    $cartItems = $quote->getAllItems();

    $quantityGroupsInCart = [];

    /** @var Quote\Item $item */
    foreach ($cartItems as $item) {
        $productId            = $item->getProductId();
        $product              = $this->productRepository->getById($productId);
        $productQuantityGroup = $product->getQuantityGroup();

        if ($product->getTypeId() == Configurable::TYPE_CODE) {

        $quantityGroupsInCart[$productQuantityGroup][] = $productId;

    foreach ($quantityGroupsInCart as $quantityGroupId => $quantityGroupProducts) {
        // Get number allowed for QG
        $quantityGroup = $this->quantityGroup->load($quantityGroupId);

        $minAllowed = $quantityGroup->getNumberAllowed();

        if (count($quantityGroupProducts) < $minAllowed) {
            throw new LocalizedException(__("You need to add more {$quantityGroup->getTitle()}"));

I am using LocalizedException as I don't know what else to use. All this exception does is show the message and stack trace.

Can someone please let me know what I can use to show a styled error message in the cart instead?

1 Answer 1


You can use ManagerInterface for display message in magento 2

protected $_messageManager;

public function __construct(
    \Magento\Framework\Message\ManagerInterface $messageManager
) {
    $this->_messageManager = $messageManager;

public function yourmethod() {
    $message = 'You need to add more {$quantityGroup->getTitle()}';
    $this->_messageManager->addSuccess($message); //For Success Message
    $this->_messageManager->addError($message);//For Error Message
  • Awesome. Thank you. For bonus points, could you also let me know how to redirect back to the cart from the plugin to show the message? I have used return $this->resultRedirectFactory->create()->setPath('/checkout/cart'); but this doesn't work
    – Wildcard27
    May 1, 2017 at 5:36
  • Refer this answer for redirect from plugin magento.stackexchange.com/a/155270/35758 May 1, 2017 at 6:30
  • can we get the error message, like if i login with invalid details, some error message shows, how to get that message? Oct 25, 2018 at 7:06

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