Rails 4-将ID转换为参数模型

Question

My code is errorring out when I try to insert a new record in the DB:

@user_request = UserRequest.new(user_request_params)

I have a model that belongs to another. The user selects the sub model in a dropdown, and the id is sent in json:

{"user_request"=>{"product_ids"=>["86", "79"], "sub_model_id"=>"5"}

Schema

UserRequest
  has_and_belongs_to_many :products
  has_one :sub_model

SubModel
  belongs_to :user_request

Product
  has_and_belongs_to_many :user_requests

The product is inserted into the db no problem (if I ignore the submodel), but the SubModel is not. I get this error:

ActiveRecord::UnknownAttributeError (unknown attribute: sub_model_id):
  app/controllers/user_requests_controller.rb:44:in `create'

I tried to edit the params before hand by doing this:

def user_request_params
    params.require(:user_request).permit(:sub_model_id, :product_ids => [])
    #the above line was there, added these lines:
    sub_id = params[:user_request][:sub_model_id]
    sub = SubModel.find(sub_id)
    params[:user_request].delete(:sub_model_id)
    params[:user_request][:sub_model] = sub
    params
end

which generates the following JSON:

{"user_request"=>{"product_ids"=>["86", "79"], "sub_model"=>#<SubModel id: 5, ...} 

but now I get this error:

ActiveModel::ForbiddenAttributesError (ActiveModel::ForbiddenAttributesError):

app/controllers/user_requests_controller.rb:42:in `create'

The submodel's were generated before hand by the admin of the site (they do exist).

How do I get the UserRequest to save?

Answer 1

UserRequest table doesn't have sub_model_id column in DB, so it raise your error. Specify it in migration and swap associations:

UserRequest
  has_and_belongs_to_many :products
  belongs_to :sub_model

SubModel
  has_one :user_request