如何结合两种不同的Mongoid标准

class Customer
  include Mongoid::Document
  field :name, type: String
  field :age, type: Integer
  field :orders, type: Array, default: []

  def add_order(order)
    orders.push(order)
  end
end

class Order
  include Mongoid::Document
  field :name, type: String
  field :price, type: Float
  field :customer_id, type: ObjectId, ref: Customer

  belongs_to :customer
end

customer = Customer.create(name: 'John Doe', age: 30)
order1 = Order.create(name: 'Product A', price: 10.99, customer_id: customer.id)
order2 = Order.create(name: 'Product B', price: 20.99, customer_id: customer.id)

customer.add_order(order1)
customer.add_order(order2)

puts customer.orders.inspect