Jekyll - Next and previous links with different categories - html

Question

I am using Jekyll to build a blog, I managed to successfully implement a Next and Previous links on my layouts pages (using this answer). I've added several categories (using this answer) and each page iterates through the proper categories displaying only what I want them to.
My only problem now is that Previous and Next buttons still iterate through all the posts regardless of what category they are in.
This is the code I used for the Next and Previous links on the bottom of the layout:
{% if page.previous %}
<span class="previous-link">
<a rel="prev" href="{{ page.previous.url }}">Previous Entry</a>
</span>
{% endif %}
{% if page.next %}
<span class="next-link">
<a rel="next" href="{{ page.next.url }}">Next Entry</a>
</span>
{% endif %}
Is there a way to make the Next and Previous buttons go to the next or previous post in the current posts' category?

Answer 1

After a bit of research. I found exactly what I was looking for on this blogpost - http://ajclarkson.co.uk/blog/jekyll-category-post-navigation/
Just needed to add a plugin to the _plugin directory and add this bit of code in it:
module Jekyll
class WithinCategoryPostNavigation < Generator
def generate(site)
site.categories.each_pair do |category, posts|
posts.sort! { |a,b| b <=> a}
posts.each do |post|
index = posts.index post
next_in_category = nil
previous_in_category = nil
if index
if index < posts.length - 1
next_in_category = posts[index + 1]
end
if index > 0
previous_in_category = posts[index - 1]
end
end
post.data["next_in_category"] = next_in_category unless next_in_category.nil?
post.data["previous_in_category"] = previous_in_category unless previous_in_category.nil?
end
end
end
end
end
And instead of using page.next.url and page.prev.url in the HTML, just use page.next_in_category.url and page.previous_in_category.url.
I hope this helps anyone experiencing the same issue.

Answer 2

The ajclarkson plugin for pagination within categories is a correct and useful solution if you are able to install plugins.
If you want to deploy to Github pages, you cannot use plugins.
I use this method to paginate within categories. This makes sure that a post from a different category will never show up:
{% if page.next and page.next.categories contains "blog" %}
Next Post
{% else if page.previous and page.previous.categories contains "blog" %}
Previous Post
{% endif %}
Be aware, this solution will not find a next post if it would have to skip over something from a different category. It avoids the worst (?) scenario, which is linking to something unintentional/not-really-a-post.