Helper module for denormalizing association attributes in Mongoid models. Why denormalize? Read A Note on Denormalization.
Extracted from coookin', where it is used in production.
Add the gem to your Bundler Gemfile:
gem 'mongoid_denormalize'
Or install with RubyGems:
$ gem install mongoid_denormalize
In your model:
# Include the helper method
include Mongoid::Denormalize
# Define your denormalized fields
denormalize :name, :email, :from => :user
class User
include Mongoid::Document
include Mongoid::Denormalize
has_many :comments
field :name
field :email
denormalize :name, :email, :to => :comments
end
class Comment
include Mongoid::Document
include Mongoid::Denormalize
belongs_to :user
field :body
denormalize :name, :email, :from => :user
end
>> user = User.create(:name => "John Doe", :email => "[email protected]")
>> comment = Comment.create(:body => "Lorem ipsum...", :user => user)
>> user.comments << comment
>> comment.user_name
"John Doe"
>> comment.user_email
"[email protected]"
>> user.update_attributes(:name => "Bill")
>> comment.user_name
"Bill"
Denormalization can happen in either or both directions. When using the :from option, the associated objects will fetch the values from
the parent. When using the :to option, the parent will push the values to its children.
# Basic denormalization. Will set the user_name attribute with the associated user's name.
denormalize :name, :from => :user
# Basic denormalization. Will set the user_name attribute of "self.comments" with "self.name".
denormalize :name, :to => :comments
# Multiple fields. Will set the user_name and user_email attributes with the associated user's name and email.
denormalize :name, :email, :from => :user
# Multiple children. Will set the user_name attribute of "self.posts" and "self.comments" with "self.name".
denormalize :name, :to => [:posts, :comments]
You must specify the type of all denormalizations when using the :from option, unless the denormalized type is String, the default.
# in User
field :location, :type => Array
denormalize :location, :to => :posts
# in Post
denormalize :location, :type => Array, :from => :user
A rake task is included for verifying and repairing inconsistent denormalizations. This might be useful your records may be modified without Mongoid, or if you are using relational associations in combination with embedded records (see Known issues).
rake db:denormalize
This task will only update records that have outdated denormalized fields.
Relational associations in combination with embedded records
It is not recommended nor supported to use mongoid_denormalize to perform denormalization to embedded records through a relational association because MongoDB/Mongoid do not support direct access to embedded fields via a relational association.
So, if User has_many :posts and User has_many :comments, but Comments are embedded_in :post, a user can't directly access a comment.
- hubsmoke (https://github.com/hubsmoke)
- Leo Lou (https://github.com/l4u)
- Austin Bales (https://github.com/arbales)
Copyright (c) 2010 Logan Raarup, released under the MIT license.