How can I show the child category and not it's parent - but other times show it's parent?

Question

I have a categories field on an entry that can have one or many children. I am able to output everything - but would like to restrict the field a bit more.

If a child has been selected, I do not want to show the parent. In my example, I only want to show "child".

It is possible, that I might only choose "parent" and I only want that to show. Or, is there a different way I should go about doing this? Thank you for any suggestions!

I've tried something like this:

{% for service in entry.servies %}
   {% set subCategories = craft.categories.descendantOf(service) %}

   {% if subCategories|length %}
       ...
   {% endif %}
{% endfor %}

But that will show the child category if it's selected or not. I would only like to show the "Child" category if it was actually selected. Otherwise, show the "parent" category.

UPDATE/SOLUTION

First, I want to thank Robin for your help. I tried different variations and was unsuccessful. I ended up taking my existing category and making it a structure. This gave me the flexibility that I needed.

Answer 1

You can change the sort order in your CategoryQuery

{% set child = entry.getFieldValue('servies').orderBy('level DESC').one() %}

returns the category of the deepest level -> the child. If no child is selected you'll receive the parent

Answer 2

Instead of a category, try creating each service within a structure. Then use an entries field to establish the relationship within the CP.

Answer 3

You can get the highest level of categories in your field and then filter your field only on that level.

{% set level = 0 %}
{% for productCategory in block.productCategories.all %}
    {% set level = productCategory.level > level ? productCategory.level : level %}
{% endfor %}

{% for productCategory in block.productCategories.level(level).all %}
    Do somestuff
{% endfor %}

Answer 4

You could loop through the selected categories, collect their ancestors and exclude them from the final entry query.

This syntax is wrong but something like:

{% set services = entry.services %}
{% set ancestors = [] %}

{% for service in services %}
  {% set ancestors = ancestors|merge(service.getAncestors()) %}
{% endfor %}

{% set mostSpecificServiceCategories = craft.categories(services).without(ancestors) %}

{% set entries = craft.entries.services(mostSpecificServiceCategories) %}