How can I automatically render partials using markdown in Rails 3?

Question

I want to have some of my partials as markdown snippets. What is the easiest way to render them using the standard rails erb templating?

Ideally, I'd like to do something like this:

If I have a partial in app/views/_my_partial.md.erb:

My awesome view
===============

Look, I can **use** <%= language %>!

which I reference from a view like so:

<%= render "my_partial", :language => "Markdown!" %>

I want to get output that looks like this:

<h1>My awesome view</h1>
<p>Look, I can <strong>use</strong> Markdown!</p>

Answer 1

Turns out, the Right Way (tm) to do this is using ActionView::Template.register_template_handler:

lib/markdown_handler.rb:

require 'rdiscount'

module MarkdownHandler
  def self.erb
    @erb ||= ActionView::Template.registered_template_handler(:erb)
  end

  def self.call(template)
    compiled_source = erb.call(template)
    "RDiscount.new(begin;#{compiled_source};end).to_html"
  end
end

ActionView::Template.register_template_handler :md, MarkdownHandler

If you require 'markdown_handler' in your config/application.rb (or an initializer), then any view or partial can be rendered as Markdown with ERb interpolation using the extension .html.md:

app/views/home/index.html.md:

My awesome view
===============

Look, I can **use** <%= @language %>!

app/controllers/home_controller.rb:

class HomeController < ApplicationController
  def index
    @language = "Markdown"
  end
end

Answer 2

Not a pure markdown solution but you can use HAML filters to render markdown, as well as other markup languages.

For example, in app/views/_my_partial.html.haml:

:markdown
  My awesome view
  ===============

  Look, I can **use** #{language}!

Answer 3

Piling on the solutions already presented, this is an interpolation-ary way in Rails 3 to render a pure Markdown file in a view from a partial without unnecessary indentation using Haml's :markdown filter and the RDiscount gem. The only catch is that your Markdown file is a Haml file, but that shouldn't matter for someone like a copy person.

In Gemfile:

gem 'rdiscount'

In app/views/my_page.html.haml

:markdown
  #{render 'my_partial', language: 'Markdown!'}

In app/views/_my_partial.html.haml

My awesome view
===============

Look, I can **use** #{language}!

If you didn't need the :language variable passed in to the markdown file, you could do away altogether with your Markdown being a Haml file:

In app/views/my_page.html.haml

:markdown
  #{render 'my_partial.md'}

In app/views/_my_partial.md

My awesome view
===============

Sorry, cannot **use** #{language} here!

Don't like those pesky underscores on your Markdown files?

In app/views/my_page.html.haml

:markdown
  #{render file: 'my_markdown.md'}

In app/views/my_markdown.md

My awesome view
===============

Sorry, cannot **use** #{language} here!

Answer 4

Have found way not to use haml in such situation.

in views/layouts/_markdown.html.erb

<%= m yield %>

in app/helpers/application_helper.rb

def m(string)
   RDiscount.new(string).to_html.html_safe
end  

in Gemfile

gem 'rdiscount'

So, in view you can call it like:

<%= render :partial => "contract.markdown", :layout => 'layouts/markdown.html.erb' %>

And contract.markdown will be formatted as markdown

Answer 5

I just released a markdown-rails gem, which handles .html.md views.

You cannot chain it with Erb though -- it's only for static views and partials. To embed Ruby code, you'd have to use tjwallace's solution with :markdown.

Answer 6

Leveraged your answer to make a gem to render for GitHub Flavored Markdown in Rails (via HTML::Pipeline): https://github.com/afeld/html_pipeline_rails

Answer 7

Here is a version similar to @Jacob's but using Redcarpet.

module MarkdownHandler
  def self.erb
    @erb ||= ActionView::Template.registered_template_handler(:erb)
  end

  def self.call(template)
    options = {
      fenced_code_blocks:           true,
      smartypants:                  true,
      disable_indented_code_blocks: true,
      prettify:                     true,
      tables:                       true,
      with_toc_data:                true,
      no_intra_emphasis:            true
    }
    @markdown ||= Redcarpet::Markdown.new(Redcarpet::Render::HTML, options)
    "#{@markdown.render(template.source).inspect}.html_safe"
  end
end
ActionView::Template.register_template_handler :md, MarkdownHandler

Full credit to lencioni who posted this in this gist.

And if you'd like to evaluate erb:

erb = ERB.new(template.source).result
@markdown ||= Redcarpet::Markdown.new(Redcarpet::Render::HTML, options)
"#{@markdown.render(erb).inspect}.html_safe"

Answer 8

You can use embedded Markdown in Rails 5. Embedded Markdown is based on the solution provided by Jacob above

1. Add these to your application's Gemfile:

    gem 'coderay' #optional for Syntax Highlighting
    gem 'redcarpet'
    gem 'emd'

2. bundle install.

3. Then create a view app/view/home/changelog.html.md and paste your markdown in that .md file.

4. Generate a home controller using the following command

   rails generate controller home

5. Add the following line to your route.rb:

   get '/changelog', :to 'home#changelog'

6. That's all. Visit http://localhost:3000/changelog to see your rendered markdown

Source: http://github.com/ytbryan/emd