Code Quality Rank: L5
Monthly Downloads: 10,498
Programming language: Ruby
License: MIT License
Tags: Misc    
Latest version: v2.0.1

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AutoHtml is a collection of filters that transforms plain text into HTML code.


Add this line to your application's Gemfile:

gem 'auto_html'

And then execute:

$ bundle

Or install it yourself as:

$ gem install auto_html


AutoHtml uses concepts found in "Pipes and Filters" processing design pattern:

  • Filter - transforms an input. In AutoHtml context, this is any object that does the transformation through #call(String) method. Filter options should be passed in initializer. AutoHtml provides some filters already, ie Link, Image, Markdown, etc.
  • Pipeline - a composition of filters that transforms input by passing the output of one filter as input for the next filter in line. In AutoHtml context, this is the AutoHtml::Pipeline class. Since the same interface (method #call) is used to pass input, we can say that Pipeline is just another Filter, which means it can be used as a building block for other Pipelines, in a mix with other filters.


link_filter = AutoHtml::Link.new(target: '_blank')
link_filter.call('Checkout out my blog: http://rors.org')
# => 'Checkout out my blog: <a target="blank" href="http://rors.org">http://rors.org</a>'

emoji_filter = AutoHtml::Emoji.new
emoji_filter.call(':point_left: yo!')
# => '<img src="/images/emoji/unicode/1f448.png" class="emoji" title=":point_left:" alt=":point_left:" height="20" witdh="20" align="absmiddle" /> yo!'

# Use Pipeline to combine filters
base_format = AutoHtml::Pipeline.new(link_filter, emoji_filter)
base_format.call('Checkout out my blog: http://rors.org :point_left: yo!')
# => 'Checkout out my blog: <a href="http://rors.org">http://rors.org</a> <img src="/images/emoji/unicode/1f448.png" class="emoji" title=":point_left:" alt=":point_left:" height="20" witdh="20" align="absmiddle" /> yo!'

# A pipeline can be reused in another pipeline. Note that the order of filters is important - ie you want
# `Image` before `Link` filter so that URL of the image gets transformed to `img` tag and not `a` tag.
comment_format = AutoHtml::Pipeline.new(AutoHtml::Markdown.new, AutoHtml::Image.new, base_format)
comment_format.call("Hello!\n\n Checkout out my blog: http://rors.org :point_left: yo! \n\n http://gifs.joelglovier.com/boom/booyah.gif")
# => "<p>Hello!</p>\n\n<p>Checkout out my blog: <a href="<img src="http://rors.org" target="_blank">http://rors.org</a> <img src="/images/emoji/unicode/1f448.png" />" class="emoji" title=":point_left:" alt=":point_left:" height="20" witdh="20" align="absmiddle" /> yo! </p>\n\n<p><a href="<img src="http://gifs.joelglovier.com/boom/booyah.gif" />" target="_blank"><img src="http://gifs.joelglovier.com/boom/booyah.gif" /></a></p>\n"

Bundled filters

Bellow is the list of bundled filters along with their optional arguments on initialization and their default values.

  • AutoHtml::Emoji, width: 20, height: 20, asset_root: '/images'
  • AutoHtml::HtmlEscape
  • AutoHtml::Image, proxy: nil, alt: nil
  • AutoHtml::Link, target: nil, rel: nil
  • AutoHtml::Markdown
  • AutoHtml::SimpleFormat

Using AutoHtml with ActiveRecord

For performance reasons it's a good idea to store the formated output in the database, in a separate column, to avoid generating the same content on each access. This can be acomplished simply by overriding the attribute writter:

class Comment < ActiveRecord::Base
  FORMAT = AutoHtml::Pipeline.new(

  def text=(t)
    self[:text_html] = FORMAT.call(t)

Now, every time text attribute is set, text_html will be set as well:

comment = Comment.new(text: 'Hey!')
comment.text_html # => '<p>Hey!</p>'


AutoHtml is released under the MIT License.

*Note that all licence references and agreements mentioned in the auto_html README section above are relevant to that project's source code only.