NoBrainer References

An alternative to ActiveRecord-style associations using idiomatic Ruby.

Design

ActiveRecord provides associations between models as a convenient interface to SQL's use of relations between table rows, and NoBrainer matches this functionality. But they are fundamentally different to the way that Ruby and most programming languages store relationships between models: references.

Installation

Add the Ruby gem to your Gemfile:

$ bundle add nobrainer-references

Example

class Publisher
  include NoBrainer::Document
  field :name, type: String
end

class Person
  include NoBrainer::Document
  field :name, type: String
end

class Book
  include NoBrainer::Document
  field :title, type: String
  references_many :authors, model: Person
  references_one  :publisher
end

douglas_adams = Person.create!(name: "Douglas Adams")
john_lloyd = Person.create!(name: "John Lloyd")
publisher = Publisher.create!(name: "Pan Books")
book = Book.create!(
  title: "The Meaning of Liff",
  authors: [douglas_adams, john_lloyd],
  publisher: publisher
)

...

book = Book.where(title: "The Meaning of Liff").first
book.publisher.name         #=> "Pan Books"
book.authors.map(&:name)    #=> [ "Douglas Adams", "John Lloyd" ]

How It Works

This gem adds a NoBrainer field type that's a Reference to a model of a particular type. This type acts as a lazy-loading delegator, which serializes the referred object by its id when saving the model, and then later loads that object when it's dereferenced (or is eager-loaded).

references_one and references_many are convenience methods for creating fields with the correct types and default names according to convention:

references_one  :publisher
# ... same as ...
field :publisher, type: Reference.to(Publisher), store_as: 'publishder_id'

references_many :authors, model: Person
# ... same as ...
field :authors, type: Array.of(Reference.to(Person)), store_as: 'author_ids'

It also supports eager-loading of references:

book = Book.eager_load(:authors, :publisher).where(title: "The Meaning of Liff").first
book.authors(&:map)   #=> [ "Douglas Adams", "John Lloyd" ]

Future Plans

• Add a referenced_by convenience method for tracking which other models/fields reference this one. Provides parity with the ActiveRecord belongs_to/has_many inverse associations. This would be installed automatically by the references_one and references_many convenience methods.

• Use reference tracking to implement garbage collection.