How to combine for and where clause in Liquid - shopify

Question

I'm currently working on a shopify site and need to create a filter on a products page. My goal is to have primer paints show up in a different section of the product collection page. What I'm having trouble with is how to filter for primers. We have a tag set up in the product page named "Primer". What I want is for the loop to check whether a product has the primer tag, and if so, display that as one of the products in the loop. I'm relatively new to Liquid, so I don't know how to combine clauses if that's possible. I've looked up the "Where" clause, but don't entirely understand how it works.
Here is the code as it stands:
<div class="{% if settings.show_collection_sidebar %}desktop-10{% else
%}desktop-12{% endif %} tablet-6 mobile-3" id="bside">
<div id="product-loop">
{% for product in collection.products %}
<div class="product {% if settings.products_per_row == '3' %}
desktop-4{% cycle ' first', '', ' last' %}
{% elsif settings.products_per_row == '4' %}
desktop-3{% cycle ' first', '', '', ' last' %}
{% endif %} tablet-half mobile-half"
id="prod-{{ product.id }}"
data-alpha="{{ product.title }}"
data-price="{{ product.price }}">
{% include 'product-listing' %}
</div>
{% endfor %}
</div>
</div>
How could I filter for the desired results? I've tried {% if product.tags contains 'Primer' %} in quite a few places, but to no avail.
Thanks for your help.

Answer 1

Have you considered using two collections to accomplish what you're after?
If you made a dynamic ("Smart") collection for all your primers (Let's assume the handle for the collection is 'primer'), you can access that collection at any time through Liquid:
{% assign primer_collection = collections['primer'] %}
{% for product in primer_collection.products %}
<h2>HAVE SOME {{ product.title }}!</h2>
{% endfor %}
Then, if you wanted to exclude all of your primer products from the main collection, create a collection named 'all' (or at least with the handle 'all' - the actual title doesn't strictly matter - see footnote). By default, the 'All' collection is, true to its name, every product in your store. However, if you create your own 'all' collection, you can define it to mean "Everything except certain items" - in your case, 'everything but the primer'
Having Shopify pre-filter everything for you through the collections themselves greatly reduces the headaches of trying to apply filters after-the-fact and dealing with misleading item counts, uneven pagination, etc.
Handles: At the bottom of each collection and product in your Shopify admin is the SEO settings. Editing these allows you to change what the handle for the collection/product is, and this is what Shopify uses to look up your collection/product internally