Impossible to access an attribute (“username”) on a NULL variable (“”)

Question

Trying to display the username of the logged in user by putting

{{ app.user.username }}

in base.html.twig gives me an error like

Answer 1

Try to check first if user exists, and then get its username:

{% if app.user %}
    {{ app.user.username }} 
{% endif %}

or do it with ternary operator:

{{ app.user ? app.user.username }} 

You could use default Twig filter to set default value if username is empty:

 {{ app.user.username|default('undefined') }}