AssociationTypeMisMatch:如何使用接受JSON的RESTful API(Rails)创建对象和关联

Question

我已经尝试了几个小时，但我似乎不明白我做错了什么。为了便于演示，我简化了我的示例。

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

给定类别汽车和车轮

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格式良好。不考虑轮子，Car对象将被创建并持久化。然而，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)>

Answer 1

如果你想创建一辆带轮子的汽车，你需要使用accepts_nested_attributes_for

添加到车型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