Mongomapper

MongoMapper requires the mongodb be installed and running. Note this example is a little old, you probably want to use a newer version of mongomapper.

Configuration

Gemfile

gem 'mongo', '~>1.3.0'
gem 'mongo_mapper', '~>0.9.0'

model/init.rb

# Here goes your database connection and options:
require 'mongo_mapper'
require 'log4r'

# connect with a logger! Whoooop! Great feature
MongoMapper.connection = Mongo::Connection.new('localhost', nil, :logger => Log4r::Logger['charta'])
MongoMapper.database = 'charta-test'

# Use identity map for all models
module IdentityMapAddition
  def self.included(model)
    model.plugin MongoMapper::Plugins::IdentityMap
  end
end

# our mongomapper extensions
Dir[__DIR__('extensions/*.rb')].each {|name| require name}

# Here go your requires for models:
require __DIR__('card')

model/extensions/uniq_array.rb

This is an example for a custom data type, in this case an array constrained to unique values

module MongoMapper
  module Extensions
    module UniqArray
      # to_mongo gets called anytime a value is assigned
      def to_mongo(value)
        value = value.respond_to?(:lines) ? value.lines : value
        value.to_a.uniq
      end

      # from mongo gets called anytime a value is read
      def from_mongo(value)
        (value || []).uniq
      end
    end
  end
end

class UniqArray
  extend MongoMapper::Extensions::UniqArray
end

model/card.rb

This is an example model.

# This models the 3x5 card with self referencing parents and children associations
class Card
  include MongoMapper::Document
  
  key :name, String
  key :owner, User, :required => true
  key :readers, Array, :typecast => 'User', :default => []
  key :writers, Array, :typecast => 'User', :default => []
  
  key :fields, Array, :default => []

  key :card_ids, Array, :typecast => 'ObjectId', :default => []
  many :children, :in => :card_ids, :class_name => 'Card'

  key :parent_card_ids, Array, :typecast => 'ObjectId', :default => []
  many :parents, :in => :parent_card_ids, :class_name => 'Card'

  def children?
    children.size > 0
  end
  
  def parents?
    parents.size > 0
  end
  
  # Card attachment methods are self saving otherwise
  # the bidirectional parent-to-childe relationships could be
  # compromised.
   
  def attach_parent(card)
    parents << card
    card.children << self
    card.save
    save
  end
  
  def attach_child(card)
    children << card
    card.parents << self
    card.save
    save
  end
  
  def detach_parent(card)
    parents.delete(card)
    card.children.delete(self)
    card.save
    save
  end
  
  def detach_child(card)
    children.delete(card)
    card.parents.delete(self)
    card.save
    save
  end
end