A helper for defining model class for MongoDB Ruby Driver.

Blog post for it: http://huiming.io/2016/10/07/mongo-document.html

1. You want something simple yet powerfull - The mongo Gem seems fit, but you can't build model class like Mongoid does with it.
2. However you don't want to turn to Mongoid since it's far away from the simple mongo.

mongo-document is just such a tiny helper for mongo that enables you to build model class like Mongoid does.

gem install mongo-document

require 'mongo/document'

Mongo::Document.establish_connection(
  :hosts => ["localhost:27017"],
  :database => "mongo-document-test",
)

class User
  include Mongo::Document
  
  indexes.create_many([
    { :key => { :email => 1 }, :unique => true, :sparse => true },
    { :key => { :type => 1 }},
  ])
end

User.insert_one(:email => 'a@b.com', :type => 'dev', :name => 'Bob')
users = User.find(:email => 'a@b.com')
...

The model class User defines a collection named users. The mapping from class name to collection name conforms to the behaviour of ActiveRecord. You can override this by explicitly naming the collection like:

class User
  include Mongo::Document
  
  self.collection_name = 'old_users'
end

The model class User has all public methods defined in Mongo::Collection by mongo Gem. In fact the former forwards those method calls to the latter. You use the model class just as a Mongo::Collection object!

Before you call any methods of a Mongo::Collection object, you need to call Mongo::Document.establish_connection first. It takes a singel hash parameter, in which a hosts or a uri field must be provided. The uri conforms to the MongoDB document: https://docs.mongodb.com/manual/reference/connection-string/. The other fields of the spec hash are optional and documented in: https://docs.mongodb.com/ruby-driver/v2.2/tutorials/ruby-driver-create-client/#ruby-driver-client-options

What's more, if you have a config file config/database.yml under the current working directory, it will be read for a call to Mongo::Document.establish_connection automatically. That's a Rails/Rack convention. You can disable this behaviour by setting environment variable MD_NO_AUTO_CONFIG=1. The format of the file is like:

development:
  hosts:
    -- localhost:27017
  database: dev-db
  
test:
  hosts:
    -- localhost:27017
  database: test-db

The parameters are documented as mentioned above for Mongo::Document.establish_connection.

You're encouraged to open the single source file to see how slim the implementation is! Total code is less than 100 lines!