Remove duplicate data from the Twig object and combine it

In my Twig template i have list, something like this:

1985 - John
1974 - Lena
1985 - Sandra
1974 - Tom
1985 - Jess

The year can be duplicated. So i need combine my list like this:

1985 - John, Sandra, Jess
1974 - Lena, Tom

Is it possible to do this in the Twig template engine?

Solution

In Twig, we can add data to an array with the merge filter.

The tricky parts:

we have to merge the names for each year and then merge it to the main array, with the year as the key
Twig resets the key to a number (0, 1, etc.) if we try to use a number as a key

If we have this data:

{% set data = [
  {"year": 1985, "name": "John"},
  {"year": 1974, "name": "Lena"},
  {"year": 1985, "name": "Sandra"},
  {"year": 1974, "name": "Tom"},
  {"year": 1985, "name": "Jess"},
]
%}

We can loop over it, and create an array, with each year as the key and the names as values:

{% set groupedData = {} %}

{# Loop over data #}

{% for person in data -%}
    {# the year must be casted as a string, otherwise it uses numeric keys in the array #}
    {% set year = "y" ~ person["year"] %}
    {% set name = person["name"] %}
  
    {% if year not in groupedData|keys %}
        {# year doesn't exist in the array, add a key with the year and an array with one name #}
        {% set groupedData = groupedData|merge({(year): [name]}) %}
    {% else %}
        {# year exists in the array, add the name to the array of names for this year #}
        {% set newNamesForYear = attribute(groupedData, year)|merge([name]) %}
        {% set groupedData = groupedData|merge({(year): newNamesForYear}) %}
    {% endif %}
{% endfor %}

And display the result:

{% for year, names in groupedData %}
    {# remove the y in the year and print the names #}
    {{ year|slice(1) }} - {{ names|join(', ') }}
{% endfor %}

Here is the result:

1985 - John, Sandra, Jess
1974 - Lena, Tom

Try it online on TwigFiddle.

Resources used: