a·mal·ga·mate /əˈmalgəˌmāt/

To unite together (classes, races, societies, ideas, etc.) so as to form a homogeneous or harmonious whole. (Used either of combining two elements, or one element with another.)

Source: "amalgamate, v.". OED Online. December 2012. Oxford University Press. 5 February 2013 http://www.oed.com/view/Entry/5975.

Introduction

Amalgamate is an extension of ActiveRecord that facilitates merging two individual records into a single record. The intent is to provide a simple, fast, and safe method for reducing duplication within the database.

Installation

Rails 4.x

Add the following line to the project Gemfile

gem 'amalgamate', github: 'danreedy/amalgamate', branch: 'rails4'

Then run bundle install.

Usage

Making use of ActiveSupport::Concern, Amalgamate extends ActiveRecord objects to include several class methods. Refer to the documentation to see the underlining logic.

All examples will use the terms master and slave. Master being the record to keep and slave being the duplicate record.

#unify(slave, options={})

Unify is the most frequently used method. Calling master.unify(slave) will:

• Fill any nil attributes of master with the non-nil value of the same attribute of slave.
• Use the attribute of master if there is a conflict between the same attribute of slave.
• Update has_one and has_many associations of slave to reference to master.
• Call destroy on slave
• Call save on master

Options

Option	Accepted Values	Default	Description
:priority	:master, :slave	:master	Determines which object takes priority when setting attributes. If set to :slave the attribute values of slave will be used to update master
:ignore	Array of sybmols	[:id, :created_at, :updated_at]	Ignores attributes when merging.
:reassign_associations	true, false	true	Amalgamate will update has_one and has_many associations to change slave associations to point to master
:save	true, false	true	Amalgamate will call save on master
:destroy	true, false	true	Amalgamate will call destroy on slave after saving master

#diff(slave)

Diff returns a Hash containing the attributes that a different between master and slave.

Example Output

> master.first_name
=> "Dan"
> master.last_name
=> "Reedy"
> slave.first_name
=> "Daniel"
> slave.last_name
=> "Reedy"

> master.diff(slave)
=> { :first_name => { :master => "Dan", :slave => "Daniel" } }

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This project rocks and uses MIT-LICENSE.