Twig sum row above the summerisation

Question

I'm kinda new to twig and I know it is possible to add up values in a template and collect them in a variable. But what i actually need is to show the summerised value in the template before I sum up them. I need something like slots in the old symfony. Or in php I could do this by ob_start(). It is possible in twig somehow?

I whould like it something like this.

sum is: {{ sum }} {# obviously it is 0 right here, but i want the value from the calculation #}

{# some content.. #} 

{% set sum = 0 %}

{% for r in a.numbers}

   {% set sum = sum + r.number %}

{% endfor %}

Answer 1

You can extend twig by adding extra filters http://symfony.com/doc/current/cookbook/templating/twig_extension.html

In your case, you can use array_sum function:

public function getFilters()
{
    return array(
        new \Twig_SimpleFilter('sum', 'array_sum'),
    );
}

Answer 2

if you don't want to use the controller and want to do the summing in twig then try using the set command:

{# do loop first and assign whatever output you want to a variable #}
{% set sum = 0 %}    
{% set loopOutput %}               
    {% for r in a.numbers}            
       {% set sum = sum + r.number %}        
    {% endfor %}    
{% endset %}

 sum is: {{ sum }} 

{# some content.. #} 

{{ loopOutput }}

I assume the loop was in a specific place because it is intended to output something into the template, this allows you to rearrange the load order while still displaying as you want.

Answer 3

As of Twig 1.41 and 2.10 a reduce filter was added

The reduce filter iteratively reduces a sequence or a mapping to a single value using an arrow function, so as to reduce it to a single value. The arrow function receives the return value of the previous iteration and the current value of the sequence or mapping:

{% set numbers = [1, 2, 3] %}

{{ numbers|reduce((carry, v) => carry + v) }}
{# output 6 #}

The reduce filter takes an initial value as a second argument:

{{ numbers|reduce((carry, v) => carry + v, 10) }}
{# output 16 #}

Note that the arrow function has access to the current context.

Arguments:

• array: The sequence or mapping
• arrow: The arrow function
• initial: The initial value

---

Ref: https://twig.symfony.com/doc/2.x/filters/reduce.html

Answer 4

A possible solution to this would be to use the MVC standard and let your controller do the sum calculations for you.

//In your controller file

public function yourControllerAction(){
    //how ever you define $a and $content would go here

    $sum = 0;
    foreach($objects as $a)
        $sum = 0;
        foreach($a->numbers as $r){
            $sum += $r->number;
        }
        $a->sum = $sum;
    }


    return array(
        'objects' => $objects,
        'content' => $content
    );
}

Now you have the sum variable already calculated to use in your twig file:

{# twig file #}
{% for a in objects %}
    sum is: {{ a.sum }}
    {% for number in a.numbers %}
        {{number}}
    {% endfor %}
{% endfor %}
{# some content.. #}