how can i connect to a mongodb from Ruby code ?
Kir's answer is appropriate if you are working only with Ruby. But if you are developing a Rails app, you likely will want to connect to MongoDB with an ORM such as:
Using an ORM will give you the functionality Rails developers are familiar with in ActiveRecord. See a list of MongoDB Clients on http://ruby-toolbox.com/.
Short version: install the Mongo gem, then db = Mongo::Connection.new.db("mydb")
Firstly, you have to install MongoDb gem:
gem install mongo
Then run code:
require 'rubygems' # not necessary for Ruby 1.9
require 'mongo'
db = Mongo::Connection.new.db("mydb") # OR
db = Mongo::Connection.new("localhost").db("mydb") # OR
db = Mongo::Connection.new("localhost", 27017).db("mydb")