How to cycle only when date changes within array in twig?

Question

I am very new to twig and have a problem which I don't know how to solve.

So I have something like this:

{% for entry in entries %}
{% set startDate = entry.begin|date_time %}
% set endDate = entry.end|date_time %}

 <tr class="{{ cycle(['odd', 'even'], loop.index0) }}">
                <td class="text-nowrap">
                    {% block date_begin %}{{ entry.begin|date_time }}{% endblock %}
                    {% if entry.end %}
                        {% block date_end %}{{ endDatum }}{% endblock %}
                    {% endif %}
                </td>

{% endfor %}

If the entries have the same date I want the <tr> to get the same class, but how do I check if the startDate of Array.1 is the same of Array.2?

As I am not really experienced with twig I can't write much here.

Answer 1

You can't use the function cycle for this use-case.

As you want to keep track of the start_date of a previous entry, you will need to store the date in a (temporary) variable and use that variable to toggle the class when they are not the same date.

{% set is_even = true %}
{% set current_date = null %}

<table>
{% for entry in entries %}
    {# store the first start_date in current_date so we can actually compare dates #}
    {% if current_date is null %}
        {% set current_date = entry.start_date %}
    {% endif %}
    
    {# toggle the class when the dates aren't the same #}
    {% if current_date|date('U') != entry.start_date|date('U') %}
        {% set is_even = not is_even %}   
        {% set current_date = entry.start_date %}
    {% endif %}
    
    <tr class="{{ is_even ? 'even':'odd' }}">
        <td class="text-nowrap">
            {{ entry.start_date }}
        </td>
    </tr>
{% endfor %}
</table>

demo