Twig - Append string data to same variable

Question

How would you append more data to the same variable in Twig? For example, this is what I'm trying to do in Twig:

var data = "foo";
data += 'bar';

I have figured out that ~ appends strings together in Twig. When I try {% set data ~ 'foo' %} I get an error in Twig.

score 31 · Accepted Answer · edited May 23 '17 at 12:10

31

The ~ operator does not perform assignment, which is the likely cause of the error.

Instead, you need to assign the appended string back to the variable:

{% set data = data ~ 'foo' %}

See also: How to combine two string in twig?

edited May 23 '17 at 12:10

Community

1
1

answered Nov 20 '12 at 19:02

Andrew

2,770
1
22
29

This won't work `{% set itemClasses = 'item ' ~ loop.first ? 'active' %}`, but this will do `{% set itemClasses = 'item ' ~ (loop.first ? 'active') %}` – Vlad Moyseenko Mar 25 '23 at 20:33

score 0 · Answer 2 · edited Mar 14 '14 at 22:10

0

Displaying dynamically in twig

{% for Resp in test.TestRespuestasA %}        
    {% set name = "preg_A_" ~ Resp.id %}
    {% set name_aux = "preg_A_comentario" ~ Resp.id %}
    <li>{{ form_row(attribute(form, name)) }}</li>
{% endfor %}

edited Mar 14 '14 at 22:10

chopper

6,649
7
36
53

answered Mar 14 '14 at 21:50

Rodolfo Velasco

845
2
12
27

score 0 · Answer 3 · answered Aug 25 '17 at 06:06

You can also define a custom filter like Liquid's |append filter in your Twig instance which does the same thing.

$loader = new Twig_Loader_Filesystem('./path/to/views/dir');
$twig = new Twig_Environment($loader);

...
...

$twig->addFilter(new Twig_SimpleFilter('append', function($val, $append) {
    return $val . $append;
}));

Resulting in the following markup:

{% set pants = 'I\'m wearing stretchy pants!' %}
{% set part2 = ' and they\'re friggin\' comfy!' %}
{% set pants = pants|append(part2) %}

{{ pants }}

{# result: I'm wearing stretchy pants! and they're friggin' comfy! #}

IMHO I find the above sample more intuitive than the ~ combinator, especially when working on a shared codebase where people new to the syntax might get a bit mixed up.

Twig - Append string data to same variable

3 Answers3