How to list an entries selected nested categories?

Question

I have a entry field populated by categories. The number of categories an entry can have is unlimited and the categories are set up as nested categories i.e.

• first level
• ---second level

• ------third level

• first level 2

• ---second level 2
• ------third level 2

I want to be able to list out any categories selected at the third level that the entry may have selected if a certain parent category is identified. So far I have the following code. This works but lists all child categories for the identified parent instead of just the selected ones.

What am I missing?

{% set cats = entry.categories %}
{% for cat in cats %}
    {% if cat.slug == 'secondlevel1' or cat.slug == 'secondlevel2' %}
        {% set catChildren = cats.descendantOf(cat.id).descendantDist('1') %}
        {% if catChildren | length %}
            {% for childCat in catChildren %}
                {% set image = childCat.buildingBlockIcon.first() %}
                    {% if image %}
                        <img alt="{{ childCat.title }}" src="{{ image.url }}" />
                    {% endif %}
            {% endfor %}
        {% endif %}
    {% endif %}
{% endfor %}

----- EDIT Solution -----

I worked this out

by changing one line of code line 4 above from

{% set catChildren = cat.level(2).children %}

to

{% set catChildren = cats.descendantOf(cat.id).descendantDist('1') %}

Now works a treat. Any better solutions feel free to post.

Answer 1

The final solution I got to work:

{% set cats = entry.categories %}
{% for cat in cats %}
    {% if cat.slug == 'secondlevel1' or cat.slug == 'secondlevel2' %}
        {% set catChildren = cats.descendantOf(cat.id).descendantDist('1') %}
        {% if catChildren | length %}
            {% for childCat in catChildren %}
                {% set image = childCat.buildingBlockIcon.first() %}
                    {% if image %}
                        <img alt="{{ childCat.title }}" src="{{ image.url }}" />
                    {% endif %}
            {% endfor %}
        {% endif %}
    {% endif %}
{% endfor %}