From https://once.com/writebook

app/models/page.rb

@@ -0,0 +1,19 @@
+class Page < ApplicationRecord
+  include Leafable
+
+  cattr_accessor :preview_renderer do
+    renderer = Redcarpet::Render::HTML.new(ActionText::Markdown::DEFAULT_RENDERER_OPTIONS)
+    Redcarpet::Markdown.new(renderer, ActionText::Markdown::DEFAULT_MARKDOWN_EXTENSIONS)
+  end
+
+  has_markdown :body
+
+  def html_preview
+    preview_renderer.render(body_preview)
+  end
+
+  private
+    def body_preview
+      body.content.to_s.first(1024)
+    end
+end