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Rails + MongoDB Simple Demo

Installing MongoDB

brew install mongodb

Start MongoDB

mongod --config /usr/local/etc/mongod.conf &

Create a new Rails app

rails new mongodb-crud --skip-active-record

Using the mongoid gem

In Gemfile: gem 'mongoid', '~> 5.1.0'

bundle install
rails g mongoid:config

Use bootstrap

In Gemfile:

gem 'bootstrap-sass', '~> 3.3.6'
gem 'bootstrap-generators', '~> 3.3.4'

In app/assets/stylesheets/application.scss:

@import "bootstrap-variables";
@import "bootstrap-generators";
@import "bootstrap-sprockets";
@import "bootstrap";

In app/assets/javascripts/application.js: //= require bootstrap-sprockets

bundle
rails generate bootstrap:install --stylesheet-engine=scss

CRUD

rails g scaffold student first_name last_name email

in config/routes.rb: root 'students#index'

Validation

in app/models/student.rb

  validates :first_name, :last_name, presence: true
  validates :email,
    presence: true,
    uniqueness: true

Indexes

in app/models/student.rb

index({ email: 1 }, { unique: true})

rake db:mongoid:create_indexes

comment out email validation and demo

More Info

Documents

Documents are the core objects in Mongoid and any object that is to be persisted to the database must include Mongoid::Document. The representation of a Document in MongoDB is a BSON object that is very similar to a Ruby hash or JSON object. Documents can be stored in their own collections in the database, or can be embedded in other Documents n levels deep.

Exercise:

1. Add a profile to Student, using embeds_one and embedded_in (Docs). Add a couple fields to the profile, and the ability to edit it in the student form.
2. Add Friendships to Student, using embeds_many. A Friendship should refer to a student using has_one

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Fields

Even though MongoDB is a schemaless database, most uses will be with web applications where form parameters always come to the server as strings. Mongoid provides an easy mechanism for transforming these strings into their appropriate types through the definition of fields in a Mongoid::Document

If you don't define a field, the following types are not supported: BigDecimal, Date, DateTime, Range

Exercise

Add a phone number type to your student profile.

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Dynamic Fields

include Mongoid::Attributes::Dynamic

• mongoid provides dot methods, but only if attribute is set, otherwise will get a NoMethodError
• safe way to access dynamic attr is with [], []=, read_attribute, write_attribute

Exercise

1. Add fields to your profile without defining them in the model
2. Add the ability for a user to add one custom field (name & value) to their profile

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Dirty Tracking

• similar to Active Record
• changed, changed?, xxxx_changed?, changes, xxxx_change, xxxx_was

Timestamps

include Mongoid::Timestamps

Persistence

create, save similar to ActiveRecord only performs atomic updates on fields that have changed field persistence methods: inc, pop, push, unset

Resources

Mongoid Documentation Mongoid is the Ruby/Rails ODM for Mongo (replaces ActiveRecord)

More in Depth Blog Demo

Large Demo maintained by Mongoid