Rails why is my parent object not saving? - ruby-on-rails

Question

I'm quite new to rails/programming/web development, and this is the error that I'm getting:
ActiveModel::MissingAttributeError (can't write unknown attribute 'shopping_list_id')
I'm trying to save a shopping list object which is populated with Item objects after selecting specific Meal objects (with collection_check_box) and the associated Ingredient objects.
Looking through the localhost server logs, all the items are created correctly using the correct ingredients retrieved (and assigned to the current shopping list id) from the correct meal_ids - but when it comes to saving the actual shopping list I get the above error. Please see below for image of server log.
I've been stuck on this for a few days now and I've seen many posts with the same error but all seem to have quite different contexts to this issue.
Is it something to do with strong_parameters? Or are my associations wrong?
In my meals index.html.erb:
<%= form_for :shopping_list, url: shopping_lists_path do |f| %>
<%= collection_check_boxes :shopping_list, :meal_ids, Meal.all, :id, :name do |b|%>
<%= b.label class:"label-checkbox" do%>
<%=b.check_box + b.text%>
<%end%>
<% end %>
<%= f.submit "Create Shopping List" %>
<% end %>
My shopping_lists_controller:
def create
#shopping_list = ShoppingList.new(shopping_list_params)
#meals = Meal.where(id:[#shopping_list.meal_ids])
#meals.map do |meal|
meal.ingredients.map do |ingredient|
#shopping_list.items.build(name: ingredient.name, quantity: ingredient.quantity, unit: ingredient.unit, shopping_list_id: #shopping_list.id)
end
end
respond_to do |format|
if #shopping_list.save
format.html { redirect_to #shopping_list, notice: 'Shopping List was successfully created.' }
format.json { render :show, status: :created, location: #shopping_list }
else
format.html { render :new }
format.json { render json: #shopping_list.errors, status: :unprocessable_entity }
end
end
end
private
def set_shopping_list
#shopping_list = ShoppingList.find(params[:id])
end
def shopping_list_params
params.require(:shopping_list).permit(:name, {meal_ids: []})
end
My ShoppingList Model:
class ShoppingList < ApplicationRecord
has_many :items
has_many :meals
accepts_nested_attributes_for :meals
accepts_nested_attributes_for :items
end
My Item Model:
class Item < ApplicationRecord
belongs_to :shopping_list
end
My schema.rb:
create_table "ingredients", force: :cascade do |t|
t.integer "meal_id"
t.string "name"
t.float "quantity"
t.integer "unit"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.index ["meal_id"], name: "index_ingredients_on_meal_id"
end
create_table "items", force: :cascade do |t|
t.integer "shopping_list_id"
t.string "name"
t.float "quantity"
t.integer "unit"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.index ["shopping_list_id"], name: "index_items_on_shopping_list_id"
end
create_table "meals", force: :cascade do |t|
t.string "name"
t.string "description"
t.string "method"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.string "meal_image_file_name"
t.string "meal_image_content_type"
t.integer "meal_image_file_size"
t.datetime "meal_image_updated_at"
t.integer "diet"
end
create_table "shopping_lists", force: :cascade do |t|
t.string "name"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
Image of server log

Answer 1

The issue is that Meal model has belongs_to :shopping_list but it doesn't have column shopping_list_id.
So when you run
ShoppingList.create(meal_ids: ['1'])
Rails tries to create Meal model and link it back to the ShoppingList, but it can't since there is no such attribute and error tells you that ActiveModel::MissingAttributeError. To fix create a migration e.g.:
add_column :meals, :shopping_list_id, :integer

Answer 2

In the create method of shopping_lists_controller, you are using a new instance of shopping_list and using the id of that instance to create items. Since the new instance is not saved to the db, it will not have id. So you cannot use #shopping_list.id while creating items.
So either change
#shopping_list = ShoppingList.new(shopping_list_params)
to
#shopping_list = ShoppingList.create(shopping_list_params)
or do
#shopping_list = ShoppingList.new(shopping_list_params)
#shopping_list.save
You may also want to destroy this object if any exception is raised.