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)?

Joannajoanne

related issue on github: Consider an instanceof test – Mountebank

@DanLee Thanks, that's interesting but I understand why the PR has been closed without being merged as this would look like a kind of mix between PHP and Twig. – Munos

Yes indeed, it's not really the business of the view. Thought it may help if you really wanted to implement the instanceof operator. – Mountebank

See #10788638 where a test has been added in order to check the type of the variable. – Buck

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.

Joannajoanne

+1 I'd say thats a perfectly fine way to do it, you'd need some sort of conditional statement somewhere unless you wanted to create a twig extension – Kelleher

You could try to call date() like: date(my_var) ? my_var|date('d/m/Y') : my_var. – Impertinence

The 'is defined' part is called a Test in Twig. Perhaps you could add your own called a_date, and do something like {% if my_var is a_date %} ...? – Lewls

@Impertinence I dont think that'd work, I think you'll get an error. This should work ok though: {{ my_var.timestamp is defined ? my_var|date : my_var }} – Kelleher

@Kelleher yep just ran some tests and it doesn't work...the timestamp is definitely a solution! – Impertinence

Beware: twig date filter (kind of) gracefully degrades, rather than failing. It didn't fail for any of these input (´'2'´, ´'0'´, ´true´, ´false´, ´''´, ´' '´, ´not_exist´) but it gave unexpected results instead. – Agamogenesis

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.

Panel

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 %}

Interplead

Answer 4

This works for me

{% if myDate is instanceof('\DateTime') %}

Fiasco