Mongoid::Atomic¶ ↑

Atomic updates for your Mongoid models.

Add to Gemfile:

gem 'mongoid_atomic'

Include the module in models where you want it:

class User
  include Mongoid::Document
  include Mongoid::Atomic

  field :username
  field :groups, :type => Array, :default => ['users']
  field :post_count, :type => Integer
end

A simple example. To increment a post count:

u = User.where(:name => 'Bill').first
u.atomic_inc(:post_count)

.. which might fit nicely in your Post model:

class Post
  include Mongoid::Document
  ...
  references_one :user
  ...
  after_create :update_post_count
  ...
  private
  def update_post_count
    self.user.atomic_inc :post_count
  end
end

.. or join a group:

...
u.atomic_push(:groups, 'posters')

.. or remove a field:

...
u.atomic_unset(:deprecated_field)

.. or change your name:

...
u.atomic_set(:username, 'bill')

.. or do all of it at once:

...
u.atomic_update :inc => {:post_count => 1}, :set => {:username => 'bobby'}, :pushAll => {:groups => %w[rubyists developers]}

No effort is made to ensure consistency between the server and instance attributes. There’s a good reason for this: the operations are performed inside of the Mongo server and we often don’t care about the result. If you need to ensure the consistency of your attributes after an update, call the Mongoid reload method. Example:

>> u = User.first
=> #<User....>

>> u.post_count
=> 0

>> u.atomic_inc :post_count
=> nil

>> u.post_count
=> 0

>> u.reload
=> #<User....>

>> u.post_count
>= 1