Method "getFlashes" for object "Symfony\Component\HttpFoundation\Session\Session" does not exist
Please keep in mind that this post was written more than 2 years ago and might be outdated.
Quick reference for people upgrading Symfony
Error
Method "getFlashes" for object "Symfony\Component\HttpFoundation\Session\Session" does not exist
Change
app.session.getFlashes()
to
app.session.get('flashes')
Before
{% for key, message in app.session.getFlashes() %}
<div class="alert alert-{{ key }}" style="margin-top: 3px;">
<a class="close" data-dismiss="alert">×</a>
<strong>{{ ('alert_message.' ~ key)|trans }}</strong> {{ message }}
</div>
{% endfor %}
After change
{% for key, message in app.session.get('flashes') %}
<div class="alert alert-{{ key }}">
<a class="close" data-dismiss="alert">×</a>
<strong>{{ ('alert_message.' ~ key) | trans }}</strong> {{ message | trans }}
</div>
{% endfor %}
That's it