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首页 > 解决方案 > AssociationTypeMisMatch：如何使用接受 JSON 的 RESTful API (Rails) 创建对象和关联（嵌套）对象？

ruby-on-rails - AssociationTypeMisMatch：如何使用接受 JSON 的 RESTful API (Rails) 创建对象和关联（嵌套）对象？

问题描述

我已经尝试了几个小时，但我似乎无法理解我做错了什么。出于演示目的，我简化了我的示例。

Car单独创建对象是可行的，但将Wheel对象附加到它会导致ActiveRecord::AssociationTypeMisMatch.

给定 Car 和 Wheel 类

class Car < ApplicationRecord
  has_many :wheels

  validates :max_speed_in_kmh,
            :name, presence: true
end


class Wheel < ApplicationRecord
  has_one :car

  validates :thickness_in_cm,
            :place, presence: true
end

和一个 CarsController

module Api
  module V1
    class CarsController < ApplicationController

      # POST /cars
      def create
        @car = Car.create!(car_params)
        json_response(@car, :ok)
      end

      private

      def car_params
        params.permit(
          :max_speed_in_kmh,
          :name,
          { wheels: [:place, :thickness_in_cm] }
        )
      end
    end
  end
end

echo '{"name":"Kid","max_speed_in_kmh":300,"wheels":[{"thickness_in_cm":70, "place":"front"},{"thickness_in_cm":75, "place":"rear"}]}' | http POST httpbin.org/post

... "json": { "max_speed_in_kmh": 300, "name": "Kid", "wheels": [ { "place": "front", "thickness_in_cm": 70 }, { "place": "rear", "thickness_in_cm": 75 } ] }, ...

JSON 格式正确。离开轮子，Car对象被创建并持久化。但是，对于Wheel对象，控制器返回

status 500 error Internal Server Error exception #<ActiveRecord::AssociationTypeMismatch: Wheel(#70285481379180) expected, got {"place"=>"front", "thickness_in_cm"=>75} which is an instance of ActiveSupport::HashWithIndifferentAccess(#70285479411000)>

标签： ruby-on-railsjsonapinested

解决方案

如果你想和轮子一起创建汽车，你需要使用accepts_nested_attributes_for

添加到 Car 模型accepts_nested_attributes_for :wheels并将强参数更改为

  def car_params
    params.permit(
      :max_speed_in_kmh,
      :name,
      { wheels_attributes: [:id, :place, :thickness_in_cm] }
    )
  end

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