Check if a variable is a date with Twig

Question

I have an array of variables that I want to display in a Twig template and each variable can be either a string or a date.

If the variable is a date, I want to apply the date filter like this:

{{ my_var|date('d/m/Y') }}

And if it's a string I want it to display it the usual way:

{{ my_var }}

Is there any way to test if a variable is a date (ie. an instance of the PHP DateTime object)?

Answer 1

Maybe not the best way to do it, but I found a solution to my problem.

{% if my_var.timestamp is defined %}
    {{ my_var|date('m/d/Y') }}
{% else %}
    {{ my_var }}
{% endif %}

As a DateTime PHP object has a public getTimestamp method, it's a way to check if the variable is a date whether this property is set or not.

Answer 2

Michael's solution works in most cases, but there are some special cases you should consider when you want to have a universal solution.

First, an object that you test for having a getTimestamp() method doesn't have to be a DateTime instance. I can thing of many cases when the timestamp field would be useful in an object, so I would test the getTimezone() method instead.

Second, if my_var is an object having a magic __call method defined, then all such tests would turn out positive. That's why I suggest the following negative test:

{% if my_var.timezone is defined and my_var.nonExistingProperty is not defined %}
    {{ my_var|date('m/d/Y') }}
{% else %}
    {{ my_var }}
{% endif %}

The second case was the one I recently struggled with because of using Propel ORM objects. The base class has the __call method that catches all Twig is defined tests.

Answer 3

You could add a class(my_var) function, for example:

// src/AppBundle/Twig/HelperExtension.php

namespace AppBundle\Twig;

use Twig_Extension;
use Twig_SimpleFunction;

class HelperExtension extends Twig_Extension
{
    public function getFunctions()
    {
        return array(
            new Twig_SimpleFunction('class', array($this, 'getClassName')),
        );
    }

    public function getClassName($object)
    {
        if (!is_object($object)) {
            return null;
        }
        return get_class($object);
    }
}

Usage:

{% if class(my_var) == 'DateTime' %}
    ...
{% endif %}