MONGOID is an Object-Relational Mapper that enables Ruby on Rails to use the NoSQL Database MongoDB as a backend. My newest project is wholly based on MongoDB.

Here’s my little cheat sheet that acts as a quick reference during my programming sprints.

The MONGOID Cheat Sheet

Example

class User
  include Mongoid::Document
  include Mongoid::Timestamps # adds automagic fields created_at, updated_at
  references_many :posts
  embeds_one :profile, :dependent => :destroy
  field :fieldname, :type => Array / BigDecimal / Boolean / Date / DateTime
                           / Float / Hash / Integer / String / Symbol / Time

  index :fieldname
end

Relations

Embedding data in the same table:

embeds_one :profile
embeds_many :settings
embedded_in :user, :inverse_of => :settings

Referencing data in an other table:

referenced_in :user
references_one :profile, :inverse_of => user
references_many :photos, :inverse_of => user

Persistence

In order to make sure data is actually to be written to disk, you need to tell mongoid

.safely.save

Queries

.where(:amount.gt => 100, :active => true)
.any_in(:category => array)
.all_in(:category => array)
.any_of({ :shape => "round" }, { :color => "red" })
.and(:amount.gt => 100, :account_status => "active")
.excludes(:status => "blocked")
.not_in(:status => ["blocked", "unverified"])
.only(:first_name, :last_name) # only retrieve these fields
.limit(20)
.skip(100)

Order

.desc(:last_name).asc(:first_name)
.order_by(:last_name.desc, :first_name.asc, :city.desc)

Criterias

.where(:title.all => ["Sir"])
.where(:age.exists => true)
.where(:age.gt => 18)
.where(:age.gte => 18)
.where(:title.in => ["Sir", "Madam"])
.where(:age.lt => 55)
.where(:age.lte => 55)
.where(:title.ne => "Mr")
.where(:title.nin => ["Esquire"])
.where(:aliases.size => 2)
.where(:location.near => [ 22.5, -21.33 ])
.where(:location.within => { "$center" => [ [ 50, -40 ], 1 ] })

Calculations

.max(:age)
.min(:quantity)
.sum(:total)

Rake Tasks

db:create
db:create_indexes
db:drop
db:migrate
db:schema:load
db:seed
db:setup
db:test:prepare

Make sure to also check out the MONGOID docs and The Definitive Guide to MongoDB.