polymorphic_preloader

PolymorphicPreloader

This gem does exactly what it says — it preloads nested polymorphic associations on ActiveRecord objects.

Here's a common example:

class Transaction < ActiveRecord::Base
  belongs_to :user
  belongs_to :purchase, polymorphic: true
end

class Product < ActiveRecord::Base
  has_many :transactions, as: :purchase
  belongs_to :company
end

class Service < ActiveRecord::Base
  has_many :transactions, as: :purchase
  belongs_to :provider
end

Suppose we want to show all the products and services that user has purchased. Apparently we want to eager-load products with companies and services with providers. ActiveRecord won't allow you to do includes(purchase: [ :company, :provider ]). Here's where PolymorphicPreloader comes to help.

Installation

Add this line to your application's Gemfile:

gem 'polymorphic_preloader', github: 'antstorm/polymorphic_preloader', branch: 'initial-version'

And then execute:

$ bundle

Or install it yourself as:

$ gem install polymorphic_preloader

Usage

Considering the above example:

transactions = current_user.transactions.includes(:purchase)

PolymorphicPreloader.new(transactions, :purchase).preload!(product: :company, service: :provider)

TODO

• Ensure good test coverage
• Tidy up and release as a gem
• Hook into ActiveRecord for a delayed preloading and nicer interface (e.g. includes_polymorphic())