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John Jacob for Main Street

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Tables and other Advanced Formatting in Action Text (Kind of)

I work on an in house Learning Management system built in Rails. This Learning Management system allows our content team to create articles, videos and quizzes. This content is delivered through lessons for new business owners. Through these tracks they learn all they need to learn to start and run new service businesses.

Since were on rails and we needed rich text editing we reached for Action Text. Action Text gives you the solid Trix editor plug and play in your app.

Rails Action Text in Practice in our Content Library Back-end

However: Action Text / Trix doesn't support tables.

Our content team had lots of tables of information they wanted to be able to communicate. Sometimes it's hard to get across nuanced information for estimating and process without a table. We realized we needed table support in Action Text / Trix.

First Direction — Action Text Attachments

My first path was to extend the Action Text attachment model. This is what the team at Timelapse documented. Although they provided some good direction, there was nothing I could directly leverage. Also, this seems like a lot of front end complexity for a v1 of a product. Was looking for something similar. In this research I found this great Rails Conf video from Chris Oliver of Go Rails, a strongly recommended resource on Action Text attachments in general. However, decided against doing something so front end heavy (for now).

The Crazy Idea that worked: Render Code-blocks as HTML

Since this project didn't ever need a "Code Block" these articles render to a non-technical audience, why not allow any valid HTML written in a code block to render as HTML.


  • No extra front end work
  • Simple Extension of the Article Decorator
  • Very maintainable portable simple content (Just HTML)


  • Your users have to be reasonably technical to update HTML code-blocks
  • You don't get a WYSIWYG interface when editing content

I put a rough prototype and did a screen recording to get my colleagues thoughts.


All credit goes to the great Manuel Ortega for actually making my crazy idea work, he was able to build a clean implementation that solved many of the pitfalls my prototype was riddled with.

It all essentially boils down to one plain ol' ruby object — this Richtext::CodeBlocks::HtmlService object:

class Richtext::CodeBlocks::HtmlService
  ALLOWED_HTML_TAGS = ["table", "tr", "td", "th", "col", "pre", "p", "h1", "h2", "h3", "summary", "details", "row", "code"]

  # To Validate HTML tags and protect from bad formatted input
  def self.validate(html)
    errors = []
    html = Nokogiri::HTML::DocumentFragment.parse(html)"pre").each do |pre_tag|
      pre_tag_html, pre_tag_errors = self.ensure_well_formed_markup(pre_tag.text)
      errors.push(pre_tag_errors) unless pre_tag_errors.empty?
      inner_html = self.extract_inner_html_from_pre_tag(pre_tag_html)
      inner_html = self.remove_not_allowed_tags_and_attributes(inner_html)
    html =
    [html.to_html, errors.flatten.uniq]

  # To parse each code block tag and render it to HTML
  def self.render(rich_text)
    html = Nokogiri::HTML::DocumentFragment.parse(rich_text)"pre").each do |pre_tag|
      inner_html = Nokogiri::HTML::DocumentFragment.parse(pre_tag.text)
      inner_html = add_styles_to_tables(inner_html)
      advanced_code_block = "<div class='advanced-code-block'>#{inner_html.to_html}</div>"


  def self.ensure_well_formed_markup(html)
    parsed = Nokogiri::XML("<pre>#{html}</pre>")
    [parsed, parsed.errors]

  # To add our bootstrap specific classes to table elements
  def self.add_styles_to_tables(html)"table").each do |table|
      table["class"] = "table"
      table.wrap("<div class='table-responsive'></div>")

  def self.extract_inner_html_from_pre_tag(html)

  # To add error messages to mis-formatted HTML
  def self.error_messages(errors)
    readable_message = ->(e) { e.message.split(":")[3].strip rescue "" } {|e| }.uniq.join(", ")


Using the HtmlService

You can just add a method in the article model:

def formatted_body

and then call it in the view

  <%= @article.formatted_body %>


Here's the example of the editor with code blocks:
Example input

Here's the example output of that article:

Rendered output
Here's example validation being thrown to prevent you from saving bad HTML.


In Production

Obviously this repo is a very limited example, but used well in production with an extended CSS framework this can be pretty powerful in practice:
Production Example 1
Production example 2

Github Repo

This is just a basic demo rails app using this approach. Excited to get feedback from anyone else looking to explore a feature like this.

Discussion (1)

bizzibody profile image
Ian bradbury

For my project, Action Text table support would be very helpful. While I appreciate this is a bit hacky - I do love the inventiveness. Definitely one for my bookmarks.