How to use messageManager to show an error after redirect

Question

I have a Module which processes a Post action, and then redirects.

Now there are error cases, and I would like to show messages for them to the users.

I already know, that this code adds the message to the session.

$this->messageManager->addError(
   $this->_objectManager->get('Magento\Framework\Escaper')->escapeHtml($message)
);

But I dont see how to trigger the rendering.

Currently it is only shown when i execute another action, which already uses this in a working way.

Like for example the login with wrong password.

Answer 1

Not sure if this is what you are looking for, but I'm giving it a shot.
You can retrieve the messages like this:

$messages = $this->messageManager->getMessages(true);  

where messageManager is an instance of \Magento\Framework\Message\ManagerInterface.

In the core, this is used for ajax calls in order to return the error messages in the json response like this (\Magento\Catalog\Controller\Adminhtml\Category\Move):

$block = $this->layoutFactory->create()->getMessagesBlock();
...
$block->setMessages($this->messageManager->getMessages(true));
$resultJson = $this->resultJsonFactory->create();

return $resultJson->setData([
    'messages' => $block->getGroupedHtml(),
    'error' => $error
]);

For actions with output you shouldn't do anything (I think). The default.xml layout file from the Magento_Theme module already contains this block <block class="Magento\Framework\View\Element\Messages" name="messages" as="messages" template="Magento_Theme::messages.phtml"/> that should handle the messages.

[Side note]:
Don't use $this->_objectManager->get('Magento\Framework\Escaper')->escapeHtml($message). Inject in your constructor an instance of Magento\Framework\Escaper and use that.

Answer 2

You need to use object injection method on ur module action class to inject the message manager object into it, i provided an example of what u can do. Hope it helps

class Example
{
    protected $_messageManager;

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

    public function method( ) {
        ..
        $message = '...';
        $this->_messageManager->addError($message);
        ..
    }
}

Answer 3

you can also find the message manager accessible through $context that is injected into actions constructors:

class yourAction extends \Magento\Framework\App\Action\Action
{
    /** var ... */
    protected $_messageManager;

    public function __construct(Context $context)
    {
        $this->_messageManager = $context->getMessageManager();
        parent::__construct($context);
    }

Next just use as mentioned in answers above

$this->_messageManager->addError($message);

Hope it helps

Answer 4

For me it looks like you need to add special block for your messages if you want to show them in non-JS way.

For example in Magento\Checkout\view\frontend\layout\checkout_cart_index.xml there is:

<referenceContainer name="page.messages">
    <block class="Magento\Checkout\Block\Cart\ValidationMessages" name="checkout.cart.validationmessages"/>
</referenceContainer>

Magento\Checkout\Block\Cart\ValidationMessages block extends core \Magento\Framework\View\Element\Messages block which is responsible for rendering messages.

Blocks defined in default.xml are for JS messages only I believe.

Answer 5

Take a look at

vendor/magento/module-customer/view/frontend/web/js/customer-data.js

/**
 * Events listener
 */
$(document).on('ajaxComplete', function (event, xhr, settings) {
    var sections,
        redirects;

    if (settings.type.match(/post|put/i)) {
        sections = sectionConfig.getAffectedSections(settings.url);

        if (sections) {
            customerData.invalidate(sections);
            redirects = ['redirect', 'backUrl'];

            if (_.isObject(xhr.responseJSON) && !_.isEmpty(_.pick(xhr.responseJSON, redirects))) {
                return;
            }
            customerData.reload(sections, true);
        }
    }
});

As we can see, there is a built-in checking function already. If our response contains keywords: 'redirect', 'backUrl', the message will load after redirecting.

• After ajax complete, the customer will be invalidated. This will be "trigger" reloading message session.
• Checking keywords: 'redirect', 'backUrl'.