将值传递给Mongoid model.new 方法而不创建字段

Question

我想将一个值传递给与任何字段无关的Mongoid模型，该值不应存储在数据库中，而应用于一些其他操作（例如执行自定义初始化）：

class Author
    include Mongoid::Document
    embeds_many :books
    field :name, type: String
    # Create a set number of empty books associated with this author.
    def create_this_many_books(quantity)
        quantity.each do |i|
            books << Book.new
        end
    end
end
class Book
    include Mongoid::Document
    embedded_in :author
    field :title, type: String
end

现在，如何在创建新作者时创建给定数量的嵌入式空book对象：

author = Author.new(name: 'Jack London', number_of_books: 41)

在这里，:number_of_books不是Author模型中的字段，而是传递给create_this_many_books的值。最好的方法是什么？

Answer 1

将Author模型更改为

class Author
  include Mongoid::Document
  embeds_many :books
  field :name, type: String
  attr_accessor :number_of_books 
  # this is plain old ruby class member not saved to the db but can be set and get
  after_create :create_this_many_books
  def create_this_many_books
    self.number_of_books.each do |i|
      books << Book.new
    end
  end
end