Jekyll place variable inside logic expression

Question

I'm trying to do the following:

{% for post in site.categories.{{ post.designer }} %}

So that when placing the above code inside a single post, it can display a list of posts from the current post's category.

However I don't think it's working because it just keeps returning undefined. My question is, is it possible in Jekyll or Liquid to place variables inside logic expressions?

Thanks

Answer 1

I suppose that "designer" is the category of your post?
If yes, you can't get it via post.designer.

You need to use page.categories instead (according to Page variables).

A post can have more than one category, so you can't just place page.categories in your loop because it's an array.

There are two possible solutions:

1. Loop through all the categories of the post, and then do your loop for each category:

   {% for cat in page.categories %}
     <h1>{{ cat }}</h1>
     <ul>
       {% for post in site.categories[cat] %}
         <li><a href="{{ post.url }}">{{ post.title }}</a></li>
       {% endfor %}
     </ul>
   {% endfor %}
   

2. If your post has only one category, you can omit the outer loop from my first example and just use the first element of the page.categories array:

   <ul>
     {% for post in site.categories[page.categories.first] %}
       <li><a href="{{ post.url }}">{{ post.title }}</a></li>
     {% endfor %}
   </ul>
   

   or

   {% assign firstcat = page.categories | first %}
   
   <ul>
     {% for post in site.categories[firstcat] %}
       <li><a href="{{ post.url }}">{{ post.title }}</a></li>
     {% endfor %}
   </ul>