Using Markdown with Rails

I would use Redcarpet to do the markdown-html conversion. Also, I would move the conversion from the view to some other object. You could use callbacks (before_save) or use Observers.

From the docs:

markdown = Redcarpet::Markdown.new(Redcarpet::Render::HTML,
    :autolink => true, :space_after_headers => true)

markdown.render("This is *bongos*, indeed.")
#=> "<p>This is <em>bongos</em>, indeed</p>"

You probably want to store the result in another column, say @post.content_parsed so that the user can make later edits to the post, plus this way you don't need to make the conversion on every request.

This is my solution

Gemfile

gem "redcarpet"

config/initializers/markdown_renderer.rb

module MarkdownRenderer
  def self.markdown
    @@markdown ||=
      Redcarpet::Markdown.new(
        Redcarpet::Render::HTML.new(
          escape_html: true,
          hard_wrap: true,
          safe_links_only: true,
          with_toc_data: true
        ),
        autolink: true,
        fenced_code_blocks: true,
        no_intra_emphasis: true,
        space_after_headers: true,
        tables: true
      )
  end

  def self.render(text)
    markdown.render(text)
  end
end

app/helpers/application_helper.rb

def markdown(text)
  MarkdownRenderer.render(text).html_safe
end

your view

<%= markdown(@post.content) %>