class Cargo < ApplicationRecord
  has_many :destinations
  has_many :assignments
  accepts_nested_attributes_for :destinations
  accepts_nested_attributes_for :assignments
end

class Destination < ApplicationRecord
  has_one :assignment_coming_to_me,class_name: 'Assignment',foreign_key: 'arrive_destination_id'
  has_one :assignment_leaving_me,foreign_key: 'start_destination_id'
end

class Assignment < ApplicationRecord
  belongs_to :start_from,class_name: 'Destination',foreign_key: 'start_destination_id'
  belongs_to :arrive_at,foreign_key: 'arrive_destination_id'
end

提供视觉图像,就像这样

+-------------+
            +---| Destination |   
            |   +-------------+---+ <= start_from
            |                     |   +------------+ 
            |                     +---| Assignment |
            |                     |   +------------+ 
+-------+   |   +-------------+---+ <= arrive_at
| Cargo | --+---| Destination |   
+-------+   |   +-------------+---+ <= start_from
            |                     |   +------------+ 
            |                     +---| Assignment |
            |                     |   +------------+ 
            |   +-------------+---+ <= arrive_at 
            +---| Destination |   
            |   +-------------+---+
            |                     |
            .                     .
            .                     .

现在,有没有办法一次创建整个记录,给定这样的参数？ (假设目的地和分配彼此相关,就像参数数组的顺序一样)

{
  cargo: [
    destinations_attributes: [{place_id: ..},{place_id: ...},...],assignments_attributes: [{assignee_id: ..},{assignee_id: ...},]
}

我知道首先保存目的地然后迭代它们来设置Assignment的destination_id可以完成这项工作,但想知道是否有更聪明的方法.