Create a simple Jekyll-like blog in your Rails 4+ app

# app/models/blog/article.rb
class Blog::Article
  include ActiveModel::Model
  attr_accessor :title, :content, :created_at, :permalink, :author

  # Used for ATOM-feed id
  def id
    @permalink.to_i
  end

  def content
    remove_yaml_frontmatter_from @content
  end

  def excerpt
    content.split('<!--more-->').first
  end

  def more_text?
    content != excerpt
  end

  def created_at
    @created_at.to_date
  end

  def to_param
    @permalink.parameterize
  end

  # Query methods
  def self.all
    article_files.reverse.map do |file|
      self.new extract_data_from(file)
    end
  end

  def self.find_by_name(name)
    file = find_file_by(name)
    self.new extract_data_from(file)
  end

  private
  def self.article_files
    sort_by_id Dir.glob(articles_path + '/' + '*.md')
  end

  def self.sort_by_id(files)
    files.sort_by { |x| File.basename(x, '.*').to_i }
  end

  def self.find_file_by(name)
    id = article_files.index { |x| x =~ /#{name}.md/ }
    article_files[id]
  end

  def self.articles_path
    Rails.root.join('app', 'views', 'blog', 'published').to_s
  end

  # Content retrieval
  def self.extract_data_from(file)
    {
      content: File.read(file),
      permalink: File.basename(file, '.*')
    }.merge(yaml_frontmatter_metadata_from(file))
  end

  def self.yaml_frontmatter_metadata_from(file)
    YAML.load_file(file)
  end

  def remove_yaml_frontmatter_from(text)
    text.sub(/^\s*---(.*?)---\s/m, "")
  end
end

# Gemfile
gem 'redcarpet' # For the Markdown parsing
gem 'pygments.rb' # Syntax highlighting

# app/helpers/blog_helper.rb
module BlogHelper
  class HTMLwithPygments < Redcarpet::Render::HTML
    def block_code(code, language)
      Pygments.highlight(code, lexer: language)
    end
  end

  def markdown(text)
    renderer = HTMLwithPygments.new(hard_wrap: true, filter_html: true)
    options = {
      autolink: true,
      no_intra_emphasis: true,
      fenced_code_blocks: true,
      lax_html_blocks: true,
      strikethrough: true,
      superscript: true
    }
    Redcarpet::Markdown.new(renderer, options).render(text).html_safe
  end

  def preserve_markdown(text) # Used to get the indentation right in the <pre> code blocks with Haml
    preserve markdown(text)
  end
end

# app/controllers/blog/articles_controller.rb
class Blog::ArticlesController < ApplicationController
  def index
    @articles = Blog::Article.all
  end

  def show
    @article = Blog::Article.find_by_name(params[:id])
  end
end

# app/views/blog/articles/index.html.haml
- @articles.each do |article|
  %article
    %h1= link_to article.title, blog_article_path(article)
    = render partial: "meta", locals: { article: article }
    = preserve_markdown article.excerpt
    - if article.more_text?
      %p= link_to "Continue reading →", blog_article_path(article)

# app/views/blog/articles/show.html.haml
%article
  %h1= @article.title
  = render partial: "meta", locals: { article: @article }
  = preserve_markdown @article.content
  %hr
  %p.action= link_to "← Back to Overview", blog_articles_path

# app/views/blog/articles/_meta.html.haml
.meta
  %time{ pubdate: "", datetime: article.created_at }
    = l article.created_at, format: :long
  by
  = article.author

# routes.rb

# This gives you:
# /blog
# /blog/:name-of-the-article
namespace :blog do
  resources :articles, path: '', only: [:index, :show]
end

# app/views/blog/articles/index.atom.builder
atom_feed do |feed|
  feed.title("Exceptiontrap Blog")
  feed.updated(@articles[0].created_at) if @articles.length > 0

  @articles.each do |article|
    feed.entry(article, url: blog_article_url(article)) do |entry|
      entry.title(article.title)
      entry.content(markdown(article.content), type: 'html')
      entry.author do |author|
        author.name(article.author)
      end
    end
  end
end

# Before (greedy)
def remove_yaml_frontmatter_from(text)
  text.sub(/^\s*---(.*)---\s/m, "")
end

# After (non-greedy)
def remove_yaml_frontmatter_from(text)
  text.sub(/^\s*---(.*?)---\s/m, "")
end