This small, yet handy library sits on top of the Redcarpet markdown parser and adds checkbox rendering functionality simply by adding - [ ] or - [x] to your markdown (similar to how GitHub does it). To build a bare bones checkbox markdown parser:

require 'markdown_checkboxes'

parser = CheckboxMarkdown.new(Redcarpet::Render::HTML.new())

markdown = <<-MARKDOWN
# Test h1
### Test h3

* Top level list
  * Second level list

- [ ] Need to do
- [x] Done!
MARKDOWN

parser.render(markdown)

Here's the basic setup for defining your parser object:

# Initializes a Checkbox Markdown parser
CheckboxMarkdown.new(renderer, extensions = {})

You have many customizable options that you can pass in to your renderer and extensions. To see these options when declaring your parser, please view Redcarpet's main GitHub page. CheckboxMarkdown inherits from Redcarpet::Markdown, so the same constructor args will work.

Now, those checkboxes above will be visually built and clickable, but they won't actively send a request to the server to modify any data fields. To add some update action, throw in a block with some options like:

parser.render(markdown) do |data, updated_text|
  data.remote = true
  data.method = :put
  data.url = post_path(@post, post: { body: updated_text })
end

With the markdown_checkboxes DSL, you can set any attribute on the given data object, and it will get set client-side as an html 'data-(attribute)=(value)' attribute on the tag for your checkboxes. The DSL will also swap out underscores (_) for dashes (-) in your attribute names, so, for example, data.test_this will translate to "data-test-this"

The updated_text parameter that you get in the block will be the text that your body will get changed to, should that checkbox get clicked. You'll want to include this somewhere in a url attribute on the given data object.

Assuming you have your infrastructure set up accordingly, this should send an HTTP put request to your server to update your post's body, as well as fire unobtrusive javascript after the action is completed (allowing you to do things like prevent a page refresh, and other cool js things)

gem install markdown_checkboxes

rake test