Book Image

Learning Mongoid

By : Gautam Rege
Book Image

Learning Mongoid

By: Gautam Rege

Overview of this book

Mongoid helps you to leverage the power of schema-less and efficient document-based design, dynamic queries, and atomic modifier operations. Mongoid eases the work of Ruby developers while they are working on complex frameworks. Starting with why and how you should use Mongoid, this book covers the various components of Mongoid. It then delves deeper into the detail of queries and relations, and you will learn some tips and tricks on improving performance. With this book, you will be able to build robust and large-scale web applications with Mongoid and Rails. Starting with the basics, this book introduces you to components such as moped and origin, and how information is managed, learn about the various datatypes, embedded documents, arrays, and hashes. You will learn how a document is stored and manipulated with callbacks, validations, and even atomic updates. This book will then show you the querying mechanism in detail, right from simple to complex queries, and even explains eager loading, lazy evaluation, and chaining of queries. Finally, this book will explain the importance of performance tuning and how to use the right indexes. It also explains MapReduce and the Aggregation Framework.
Table of Contents (14 chapters)
Learning Mongoid
About the Author
About the Reviewers

embeds_one – embed one document

This relation takes the standard options, which we have seen earlier: :autobuild, :as, :cascade_callbacks, :cyclic, :store_as, and so on. However, it's interesting how we can manage relations using the names of the relations.

What if we want to save the relation twice in the same parent class? For example, in the Author model, we want the permanent and current addresses. Both are Address objects. We use the name option that specifies the name of the relation in which the information would be stored. Have a look at the following code:

class Author
  include Mongoid::Document

  embeds_one :permanent_address, class_name: "Address"
  embeds_one :current_address, class_name: "Address"

class Address
  include Mongoid::Document

  embedded_in :author, inverse_of: :permanent_address
  embedded_in :author, inverse_of: :current_address

If we create an author now, MongoDB stores both the addresses under different names:

{ "_id" : ObjectId("51b42d4245db7c9535000001...