{"user":["must exist"]} Error with Rails Nested Resources and Authentication - ruby-on-rails

Question

I'm relatively new to Rails and have what I think is a relatively straightforward set-up that I'd like to use. I have users, lists, and items. Each user has many lists and each list has many items. I'm having trouble creating items after logging in.
User model:
class User < ApplicationRecord
include Authentication
has_many :examples
has_many :lists
has_many :items
end
List model:
class List < ApplicationRecord
belongs_to :user
has_many :items
end
Item model:
class Item < ApplicationRecord
belongs_to :user
belongs_to :list
end
Here are the relevant routes:
Rails.application.routes.draw do
resources :lists do
resources :items
end
I can create/read/update/delete lists with the following controller:
class ListsController < ProtectedController
before_action :set_list, only: [:show, :update, :destroy]
# GET /lists
def index
#lists = current_user.lists
render json: #lists
end
# GET /lists/1
def show
render json: List.find(params[:id])
end
# POST /lists
def create
#list = current_user.lists.build(list_params)
if #list.save
render json: #list, status: :created, location: #list
else
render json: #list.errors, status: :unprocessable_entity
end
end
# PATCH/PUT /lists/1
def update
if #list.update(list_params)
render json: #list
else
render json: #list.errors, status: :unprocessable_entity
end
end
# DELETE /lists/1
def destroy
#list.destroy
end
private
# Use callbacks to share common setup or constraints between actions.
def set_list
#list = current_user.lists.find(params[:id])
end
# Only allow a trusted parameter "white list" through.
def list_params
params.require(:list).permit(:name)
end
end
However, I can't create an item successfully. Here is my item controller:
class ItemsController < ProtectedController
before_action :set_item, only: [:show, :update, :destroy]
# GET /items
def index
#items = current_user.items
render json: #items
end
# GET /items/1
def show
render json: #item
end
# POST /items
def create
#list = List.find(params[:list_id])
#item = #list.items.create(item_params)
if #item.save
render json: #item, status: :created, location: #item
else
render json: #item.errors, status: :unprocessable_entity
end
end
# PATCH/PUT /items/1
def update
if #item.update(item_params)
render json: #item
else
render json: #item.errors, status: :unprocessable_entity
end
end
# DELETE /items/1
def destroy
#item.destroy
end
private
# Use callbacks to share common setup or constraints between actions.
def set_item
#item = current_user.items.find(params[:id])
end
# Only allow a trusted parameter "white list" through.
def item_params
params.require(:item).permit(:name, :quantity, :price, :store, :category, :notes, :user_id, :list_id)
end
end
I sign in, create a list, and then try to post an item to that list but get the following error:
{"user":["must exist"]}
Here is the message from the server:
Started POST "/lists/4/items" for 127.0.0.1 at 2017-08-09 22:47:19 -0400
Processing by ItemsController#create as */*
Parameters: {"item"=>{"name"=>"Test Item", "quantity"=>"1", "price"=>"9.99", "store"=>"Fruit Center", "category"=>"Dairy", "notes"=>"Important Note"}, "list_id"=>"4"}
User Load (0.3ms) SELECT "users".* FROM "users" WHERE "users"."token" = $1 LIMIT $2 [["token", "27e3e2a67d86cb9d3f46d20651370b74"], ["LIMIT", 1]]
List Load (0.3ms) SELECT "lists".* FROM "lists" WHERE "lists"."id" = $1 LIMIT $2 [["id", 4], ["LIMIT", 1]]
(0.1ms) BEGIN
(0.2ms) COMMIT
(0.1ms) BEGIN
(0.1ms) ROLLBACK
[active_model_serializers] Rendered ActiveModel::Serializer::Null with ActiveModel::Errors (0.06ms)
Completed 422 Unprocessable Entity in 8ms (Views: 0.5ms | ActiveRecord: 1.1ms)
Alternatively, I've tried changing the Create action for item to be this:
def create
#item = current_user.items.create(item_params)
if #item.save
render json: #item, status: :created, location: #item
else
render json: #item.errors, status: :unprocessable_entity
end
end
Doing it this way, results in a slightly different error: {"list":["must exist"]}
From the server:
Started POST "/lists/4/items" for 127.0.0.1 at 2017-08-09 23:09:20 -0400
Processing by ItemsController#create as */*
Parameters: {"item"=>{"name"=>"Test Item", "quantity"=>"1", "price"=>"9.99", "store"=>"Fruit Center", "category"=>"Dairy", "notes"=>"Important Note"}, "list_id"=>"4"}
User Load (0.1ms) SELECT "users".* FROM "users" WHERE "users"."token" = $1 LIMIT $2 [["token", "27e3e2a67d86cb9d3f46d20651370b74"], ["LIMIT", 1]]
(0.1ms) BEGIN
(0.2ms) COMMIT
(0.1ms) BEGIN
(0.1ms) ROLLBACK
[active_model_serializers] Rendered ActiveModel::Serializer::Null with ActiveModel::Errors (0.07ms)
Completed 422 Unprocessable Entity in 32ms (Views: 2.2ms | ActiveRecord: 4.1ms)
It does appear that the list_id is getting passed through in the parameters, but it's not being picked up in the create method.
I feel like I may be missing something simple. Any ideas?

Answer 1

Notice in your log that list_id is not inside of the item params:
Parameters: {"item"=>{"name"=>"Test Item", "quantity"=>"1", "price"=>"9.99", "store"=>"Fruit Center", "category"=>"Dairy", "notes"=>"Important Note"}, "list_id"=>"4"}
params[:list_id] # => 4
params[:item][:list_id] # => nil
You have white listed params[:item][:list_id] in your item_params, but list_id is not nested in params[:item] because in your item form you do not have a field to pass it along (would need a form input with name='item[list_id]'). Instead params[:list_id] = 4 is being set for the request based on the route /lists/4/items. You can do
def create
#item = current_user.items.build(item_params)
#item.list_id = params[:list_id]
if #item.save
render json: #item, status: :created, location: #item
else
render json: #item.errors, status: :unprocessable_entity
end
end
Note that I have called current_user.items.build instead of current_user.items.create. Using current_user.items.create will attempt to save the record immediately which you don't want to do in this case (it seems).