mongoid_denormalize

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mongoid_denormalize

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Helper module for denormalizing association attributes in Mongoid models.

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Mongoid::Denormalize
====================

*Note: I am no longer actively maintaining this module, and I do not know whether it is compatible with newer versions of mongoid. If you would like to take ownership of this repository, please let me know.*

Helper module for denormalizing association attributes in Mongoid models. Why denormalize? Read *[A Note on Denormalization](http://www.mongodb.org/display/DOCS/MongoDB+Data+Modeling+and+Rails#MongoDBDataModelingandRails-ANoteonDenormalization)*.

Extracted from [coookin'](http://coookin.com), where it is used in production.

Installation
------------

Add the gem to your Bundler `Gemfile`:

gem 'mongoid_denormalize'

Or install with RubyGems:

$ gem install mongoid_denormalize

Usage
-----

In your model:

# Include the helper method
    include Mongoid::Denormalize
    
    # Define your denormalized fields
    denormalize :name, :email, :from => :user

Example
-------

class User
      include Mongoid::Document
      include Mongoid::Denormalize

has_many :comments
      has_many :moderated_comments, :class_name => "Comment", :inverse_of => :moderator

field :name
      field :email
      
      denormalize :name, :email, :to => :comments
    end
    
    class Comment
      include Mongoid::Document
      include Mongoid::Denormalize

belongs_to :user
      belongs_to :moderator, :class_name => "User", :inverse_of => :moderated_comments

field :body
      
      denormalize :name, :email, :from => :user
    end
    
    >> user = User.create(:name => "John Doe", :email => "john@doe.com")
    >> comment = Comment.create(:body => "Lorem ipsum...", :user => user)
    >> user.comments << comment
    >> comment.user_name
    "John Doe"
    >> comment.user_email
    "john@doe.com"
    >> user.update_attributes(:name => "Bill")
    >> comment.user_name
    "Bill"

Options
-------

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 of "self.comments" to the value of "self.name".
    denormalize :name, :to => :comments

# Multiple children. Will set the user_name attribute of "self.posts" and "self.comments" with "self.name".
    denormalize :name, :to => [:posts, :comments]

# Basic denormalization, obeying :inverse_of. Will set the moderator_name attribute of "self.moderated_comments"
    denormalize :name, :email, :to => :moderated_comments

# With custom field name prefix. Will set the commenter_name attribute of "self.comments" (takes precedence over
    # inverse_of).
    denormalize :name, :to => :comments, :as => :commenter
    denormalize :name, :from => :comments, :as => :commenter

# Basic denormalization. Will set the user_name attribute with the associated user's name.
    denormalize :name, :from => :user

# Multiple fields. Will set the user_name and user_email attributes with the associated user's name and email.
    denormalize :name, :email, :from => :user

# Basic denormalization. Will set the moderator_name attribute with the associated author user's name.
    denormalize :name, :from => :moderator

When using `:from`, if the type of the denormalized field is anything but `String` (the default),
you must specify the type with the `:type` option.

# in User
    field :location, :type => Array
    denormalize :location, :to => :posts
    
    # in Post
    denormalize :location, :type => Array, :from => :user

A few notes on behavior:

`:from` denormalizations are processed as `before_save` callbacks.

`:to` denormalizations are processed as `after_save` callbacks.

With `:to`, validations are not run on the object(s) containing the denormalized field(s) when they are saved.

Rake tasks
----------

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.

Known issues
------------

**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.

Contributing
-------

Clone the repository and run Bundler with `bundle install`. Use `rake -T` to view available rake tasks.

You can also use `bundle exec guard` for test driven development, if desired.

A MongoDB server is required to run the specs. Docker is an easy option:

docker run --name mongo3 -d -p 27017:27017 mongo

Contributors
-------
* hubsmoke (https://github.com/hubsmoke)
* Leo Lou (https://github.com/l4u)
* Austin Bales (https://github.com/arbales)
* Isaac Cambron (https://github.com/icambron)
* Shannon Carey (https://github.com/rehevkor5)
* Sebastien Azimi (https://github.com/suruja)
* HuffMoody (https://github.com/HuffMoody)

Credits
-------

mongoid_denormalize

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