How to colorize code in your comments using CodeRay

_comment.html.erb

<%= colorize comment.body %>

comments_helper_v1.rb

module CommentsHelper
  def coderay(text)
    text.gsub(/\<code( lang="(.+?)")?\>(.+?)\<\/code\>/m) do
      CodeRay.scan($3, $2.blank? ? :html : $2.blank? ? :html : $2).div
    end
  end
end

comments_helper_v2.rb

module CommentsHelper
  def coderay(text)
    text.gsub(/\<code( lang="(.+?)")?\>(.+?)\<\/code\>/m) do
      CodeRay.scan($3, $2.blank? ? :html : $2.blank? ? :html : $2).div
    end
  end

  def colorize(text)
    text = coderay(text)
    text = simple_format(text, {}, :sanitize => false)
    text = sanitize(text, {:tags => %w(table thead tbody tr td pre span pr p), :attributes => %w(id class style)})
    text = auto_link(text, :sanitize => false)

    text.html_safe
  end
end

Gemfile

gem 'coderay'