Jekyll: How to pass a Ruby object to a template?

Question

For example, say I'd like to generate this array:

random_numbers = []
1000.times { random_numbers << rand(2) }

And pass it to a template, so that I can access it from Liquid:

{% for num in random_numbers %} 
  ... here I'd use logic around the number to generate something.
{% endfor %}

Note: I want to generate the array dynamically in Ruby. And inside the template, I want an array that I can iterate with, I don't want a string.

How can this be done in Jekyll?

Sherrillsherrington

Answer 1

Well, you'd need a plugin: https://github.com/mojombo/jekyll/wiki/Plugins

If you were happy to put the logic in your plugin, you could do it in a custom Liquid::Tag, but your requirements sound like they'd need a generator, which is OK. I just threw this together and it seems to work as you'd like:

module Jekyll

class RandomNumberGenerator < Generator

  def generate(site)
    site.pages.each do |page|
      a = Array.new
      1000.times { a << rand(2) }
      page.data['random_numbers'] = a
    end
  end

end

end

that should go in your _plugins/ directory (as rand.rb or something). In your templates, you can then do

<ul>
    {% for number in page.random_numbers %}
        <li>{{ number }}</li>
    {% endfor %}
</ul>

Or whatever you'd like. I've assumed that you want a different set of numbers for each page - but if you want one set for the whole site, you could easily produce the array once and then either attach it to the site object or to every page.

This won't work with the automatic generation on Github Pages (they don't allow custom plugins, for obvious reasons), but that shouldn't be a problem - even if you're using Github Pages there are plenty of workarounds.

Lyautey

Great answer, thank you! I got your snippets to work. What's bugging me is that changes to the plugin don't propagate after reload (when using --auto). Any ideas? – Sherrillsherrington

So to get changes to the plugin to register, you have to manually restart Jekyll? I'm afraid I don't know at all - I think you might have to do the manual restart whilst developing. However, if there are some values that you'll regularly (or ever) adjust, I'd suggest putting them in config.yml and then accessing them from there in the plugin. You can access the config as a hash like this: 'config = Jekyll.configuration({})', and then access specific options like 'config['some setting']' or 'config['some_parent']['some_nested_setting']'. – Lyautey