embeds_many – embedding many documents

This method sets up the parent embedded relation for a single embedded child. All embedded documents are saved inside the parent document. So, when you fetch the parent document, all the embedded documents are also part of it. When we use embeds_many, the embedded documents are saved in an array inside the document. This is the most commonly used relation.

class Book
  include Mongoid::Document

  embeds_many :reviews
end

As embedded documents can be polymorphic, the :as option is supported along with the relation callbacks :before_add, :after_add, :before_remove, and :after_remove. will be discussed next.

:cascade_callbacks

As embedded documents are part of the parent, their callbacks are not automatically invoked when the parent is saved. We need to explicitly set this option if we want the embedded child document to process callbacks.

class Book
  include Mongoid::Document

  embeds_many :reviews, cascade_callbacks: true
end

:store_as

The store_as option...