Question

尝试访问父数据时出现nil错误。

模型

class Coop < ApplicationRecord
   has_many :coop_farms
   has_many :farms, through: :coop_farms
   has_many :bean_shipments, inverse_of: :coop
   accepts_nested_attributes_for :bean_shipments
end

class BeanShipment < ApplicationRecord
  belongs_to :coop
  belongs_to :location
  has_many :batch_bean_shipments
  has_many :batches, through: :batch_bean_shipments
  accepts_nested_attributes_for :batch_bean_shipments
end

控制器

class BeanShipmentsController < ApplicationController
  before_action :set_bean_shipment, only: [:show, :edit, :update, :destroy]

  # GET /bean_shipments
  # GET /bean_shipments.json
  def index
    @bean_shipments = BeanShipment.all
    @bean_shipments.each do |bean_shipment|
        puts "Coop_ID is #{bean_shipment.coop_id}"
        puts bean_shipment.coop.name
     end
  end

输出为“ COOP_ID为4” 然后“为nil：NilClass定义的方法'name'”

如果我有有效的coop.name，我不知道如何获得coop_id？我想念什么？

编辑：这是模式：

create_table "bean_shipments", force: :cascade do |t|
    t.integer "coop_id", null: false
    t.string "coop_lotcode", null: false
    t.integer "location_id"
    t.datetime "created_at", precision: 6, null: false
    t.datetime "updated_at", precision: 6, null: false
  end

create_table "coops", force: :cascade do |t|
    t.string "name", null: false
    t.datetime "created_at", precision: 6, null: false
    t.datetime "updated_at", precision: 6, null: false
  end

Answer 1

回答

数据完整性问题。在bean_shipments中有coop_id与coop表中的行不对应。

如何从子级访问父级数据

1 个答案: