How best to merge an array into an array for a relatedTo query parameter?

Question

I have 3 Matrix fields which define optional parameters for building a query:

1. A related Entries field
2. A Categories field
3. A Tags field

Any combination of them could be used, including none or all.

So I need to build a relTo array to pass into an entries query.

Given that the array might have a length of 1 or greater, it may or may not need an 'and' element.

Does that 'and' have to be first?

I'm assuming it does, so I'm doing something like this:

{# Assume the field handles here exist as **block** fields and **entry** fields #}
{% set cats = block.relCats.all() ?? null %}
{% set rels = block.relEntries.all() ?? null %}
{% set tags = block.relTags.all() ?? null %}

{% set relArr = cats ? [{
    targetElement: cats, 
    field: 'relCats'
}] : [] %}

{% set relArr = rels ? relArr|merge([{
    targetElement: rels, 
    field: 'relEntries'
}]) : relArr %}

{% set relArr = tags ? relArr|merge([{
    targetElement: tags, 
    field: 'relTags'
}]) : relArr %}

So now I have an array which could be empty or have 1, 2 or 3 elements, and which may therefore require an 'and', so I’m assuming I need to do something like this:

{# Build the relTo array #}
{% if relArr|length > 1 %}
    {% set relTo = ['and'] %}

    {% for el in relArr %}
        {% set relTo = relTo|merge([ el ]) %}
    {% endfor %}
{% else %}
    {% set relTo = relArr %}
{% endif %}

{% if relTo|length %}
    {% set entries = craft.entries.section(handle)
        .relatedTo(relTo).limit(6).all() ?? null
    %}
{% else %}
    {% set entries = craft.entries.section(handle)
        .limit(6).all() ?? null
    %}
{% endif %}

Is this right, or is there a more elegant way to build the relTo array?

I'm also now wondering if I need the {% if relTo|length %} conditional or if it's fine to pass an empty array into relatedTo, because it will just get ignored. (I guess I can test that.)

Answer 1

I've realised (I think) that I can just append 'and' to relArr and then reverse it.

{% set relArr = relArr|length > 1 ? relArr|merge(['and'])|reverse : relArr %}

Gonna try that.