Getting Started (Sinatra)

Create Git Repo

While not required, we recommend creating a Git repository for your application:

git init blog
cd blog

Commit your changes as you are following this tutorial.

Create Gemfile

Create a file named Gemfile with the following contents:

source 'https://rubygems.org'
gem 'sinatra'
gem 'mongoid'
gem 'puma'

Install Dependencies

Run the following commands to install the dependencies:

gem install bundler
bundle install

This command will generate a file named Gemfile.lock which we recommend committing to your Git repository.

Run MongoDB Locally

To develop locally with MongoDB, download and install MongoDB.

Once MongoDB is installed and running, create a file named config/mongoid.yml pointing to your deployment. For example, if you launched a standalone mongod on the default port, the following contents would be appropriate:

development:
  clients:
    default:
      database: blog_development
      hosts:
        - localhost:27017
      options:
        server_selection_timeout: 1

Use MongoDB Atlas

Instead of downloading, installing and running MongoDB locally, you can create a free MongoDB Atlas account and create a free MongoDB cluster in Atlas. Once the cluster is created, follow the instructions in connect to the cluster page to obtain the URI. Use the Ruby driver 2.5 or later format.

Create a file named config/mongoid.yml with the following contents, replacing the URI with the actual URI for your cluster:

development:
  clients:
    default:
      uri: mongodb+srv://user:pass@yourcluster.mongodb.net/blog_development?retryWrites=true&w=majority
      options:
        server_selection_timeout: 5

Basic Application

Create a file named app.rb with the following contents. First, some requires:

require 'sinatra'
require 'mongoid'

Load the Mongoid configuration file and configure Mongoid. This is done automatically when Mongoid is used with Rails, but since we are using Mongoid with Sinatra, we need to do this ourselves:

Mongoid.load!(File.join(File.dirname(__FILE__), 'config', 'mongoid.yml'))

Now we can define some models:

class Post
  include Mongoid::Document
  field :title, type: String
  field :body, type: String
  has_many :comments
end
class Comment
  include Mongoid::Document
  field :name, type: String
  field :message, type: String
  belongs_to :post
end

... and add some routes:

get '/posts' do
  Post.all.to_json
end
post '/posts' do
  post = Post.create!(params[:post])
  post.to_json
end
get '/posts/:post_id' do |post_id|
  post = Post.find(post_id)
  post.attributes.merge(
    comments: post.comments,
  ).to_json
end
post '/posts/:post_id/comments' do |post_id|
  post = Post.find(post_id)
  comment = post.comments.create!(params[:comment])
  {}.to_json
end