The document provides an introduction to using MongoDB as the database for Rails applications. It discusses how MongoDB is a document database that stores data as JSON-like documents. It then demonstrates how to set up a Rails application to use Mongoid as the ORM to interact with a MongoDB database. Models, relationships, and queries are demonstrated for a sample application to track video game achievements. The document shows how to generate models, define fields and validation, embed documents, and perform queries.

1. Rails.loves?(:mongodb) => true
A Peek Into Making Awesomely Dynamic
Applications

2. How Many Have
Experience With Rails?

3. How Many Have
Experience With
Databases?

4. How Many Have Heard
Of MongoDB?

5. MongoDB Is...
Document database (NoSql) (1)
Data is stored as BSON Objects (looks exactly like
JSON)
Gives high performance, high availability, and easy
scalability
Gives you ultimate flexibility with features like...
Sweet Data Types: Hashes and Arrays
Allows you to nest documents
Allows for dynamic document attributes
(1) Despite the word “NoSql” you can still create a relational database with MongoDB

6. MongoDB In Relational Terms
MongoDB
MySql
Document
Row
Collection
Table
Database
Database
Index
Index

7. More MongoDB Knowledge
Two types of relations:
Embedded and Referenced
No such thing as a “join”, this type of thing can be
achieved with embedded documents and linking
Has a built in aggregation framework and map
reducing support.
You still have 1-1, 1-n, n-n relations

8. What A MongoDB Documents Look Like

9. How Does Rails Talk To MongoDB?
Mongoid - A Object-DocumentMapper(ODM) (1)
(1) There are other ODM’s out there for MongoDB, MongoMapper for example. I feel Mongoid is
far and away the best one. Has a supportive and active maintainer named Durran Jordan.

10. Why Not Use ActiveRecord?
ActiveRecord does not have built in
support for MongoDB. Mongoid replaces
it.
However, it still uses ActiveModel. You
still have all the validation goodness.

11. Getting Started
Install MongoDB...Kind of important
Mac:
Windows:
http:/
/docs.mongodb.org/manual/tutorial/install-mongodb-on-windows/
Ubuntu:
http:/
/docs.mongodb.org/manual/tutorial/install-mongodb-on-ubuntu/

12. Getting Started With Rails
Generate a new Rails 4 Application

13. Modify Your Gemfile
Add the following to your gemfile, then
bundle (1)(2)
(1) Current public release of Mongoid doesn’t support Rails 4. To install Mongoid 4.0, point the
gem to the Mongoid github project.
!
(2) If your using Rails 3, use the public gem

14. Generate A Mongoid Configuration File

15. What mongoid.yml Looks Like

16. All Setup. What Kind of App Should We Make?
Let’s build an app that helps you track
video game achievements that you
completed.

17. What Models Do We Need To Create?
system: name, short_name
game: title, description, released_at,
completed_at
achievement: title, description, points,
multiplayer, completed_at

18. Let’s Build A Model
Use the Rails generator as normal.

19. What The Model Looks Like By Default
Clean model just includes Mongoid::Document to a class.

20. Lets Add Some Fields
In ActiveRecord you use migrations to add and remove
fields from tables.
In Mongoid you declare your fields right in the model class.

21. How About Some Validation

22. Lets Make Some Relations

23. The Game Model

24. The Achievement Model

25. Lets Review What We Just Did
Generated our models
Added the fields
Added validation
Made the relations

26. Let’s Have Some Fun in Console

27. Create A System
Validation works
Document Created

28. Create A Game For Our System

29. How About Another Game

30. Let’s Create An Achievement

31. How About A Multiplayer Achievement

32. So How Do These Look Stored In The Database?

33. How Do The Embedded Documents Look?

34. We Completed One Of Those Achievements, lets update it

35. Lets Store A Dynamic Field

36. Lets Review What We Just Did
We created a system called “Xbox One”.
We created a new game via our system document,
automatically creating the relation to system.
We created a new game, then created the relation to system.
We can find documents by providing the document ID.
Created a single and multiplayer achievement for a game.
Took a look and how these are stored in the database.
Updated one of the achievements as completed.
Updated a document with a dynamic field.

37. Let’s Try Some Queries

38. How about all the games that are completed?

39. How About All Games Who have Achievements With Points
Greater than 10?

40. How About Achievements In A Game With Points Bet ween
10 And 30

41. Some More Advanced Things You Can Do
Custom Validation Methods
Callbacks
Scoping
GeoNear Queries
Map Reducing
Aggregation
Obser vers

42. Some Resources
MongoDB.org - More information about
MongoDB
RubyonRails.org - Read up on Rails 4
Mongoid.org - Documentation for
Mongoid

43. Follow Me
Github - BillWatts
Twitter - @BillWatts

44. Thank You!
Get This Project @ http:/
/github.com/
BillWatts/rails_loves_mongodb_talk

45. Any Questions?