symfony - Symfony - Setting Flash and Checking in TWIG

Question

I am trying to set Flash in my controller, then check in TWIG if a Flash has been set. My problem is that TWIG always reports that my Flash has not been set and I am unsure why.

Controller:

$session->getFlashBag()->add('error', 'Does Not Exist');

TWIG:

{{ dump( app.session.hasFlash('error') ) }} //outputs false
{{ dump( app.session.getFlashBag().get('error') ) }} //outputs false

Answer 1

In Controller

$this->get('session')->getFlashBag()->set('error', 'Does Not Exist');

or 

$this->get('session')->getFlashBag()->add('error', 'Does Not Exist');

In Twig

{% for flashMessage in app.session.flashbag.get('error') %}

    {{ flashMessage }}

{% endfor %}

FYI: Doc

Answer 2

In Controller :

$this->get('session')->getFlashBag()->add('error', "User does not exists.");

In View :

{% for type, messages in app.session.flashbag.all() %}
    {% for message in messages %}
        {% if type == 'error' %}
            {{ message }}
        {% endif %}
        {# Or even with css class rendering:
            <div class="flash-{{type}}">{{message}}</div>
        #}
    {% endfor %}
{% endfor %}

Answer 3

It is worth noting that in the Symfony 3.3 and up we can use simplified version app.flashes(). Example:

{% for message in app.flashes('notice') %}
    <div class="flash-notice">
        {{ message }}
    </div>
{% endfor %}

Source

Answer 4

it s simplified in symfony 4 (it should works in 3.4 too)

Your controler :

if ($form->isSubmitted() && $form->isValid()) {
    // do some sort of processing

    $this->addFlash(
        'notice',
        'Your changes were saved!'
    );
    // $this->addFlash() is equivalent to $request->getSession()->getFlashBag()->add()

    return $this->redirectToRoute(...);
}

Twig :

{% for message in app.flashes('notice') %}
    <div class="flash-notice">
        {{ message }}
    </div>
{% endfor %}

Answer 5

Using Symfony 5. If you want to display all flashes using bootstrap class naming, simply set the flash type to the bootstrap class name (success/danger/warning... etc)

In the controller set like this:

$this->addFlash('success', 'Action completed successfully.');
or...
$this->addFlash('danger', 'An error occurred.');

In Twig display once, in a base template for example - like this (notice the simplified app.flashes array var):

{% for type, messages in app.flashes %}
    {% for message in messages %}
        <div class="alert alert-{{ type }}">{{ message }}</div>
    {% endfor %}
{% endfor %}

Answer 6

Use FlashAlertBundle, it provides a simplified way to handle (add/display) Symfony flash messages.

Available through
https://github.com/rasanga/FlashAlertBundle
https://packagist.org/packages/ras/flash-alert-bundle

You just need a single line

{{ render_flash_alerts() }}

to render flash messages

Answer 7

This question is pretty old now but I have not seen this answer yet.

For checking if a flash message with a specific type has been set:

Twig:

{% if app.session.flashBag.has('error') %}
    ...
{% endif %}

The code inside the if statement will be executed, if a message with type "error" has been set. You can use iteration inside, but this is only for checking, if a message exists.