Rails 6 table association user table in association with items table - ruby-on-rails

Question

Hi I'm trying to create an app that has items users are selling. I have a table for Users selling the item and a table for items, but I'm a little confused about how I should setup the next table for the buyer. I have a separate table that is many to many between User and Item tracking user_id and item_id. Should I be creating a similar table tracking buyer_id and item_id? I want to be able to track what item has been bought from which user and vs versa. User and Buyers are from the same User table.
Thanks!
Edit:
class UsersController < ApplicationController
def my_page
#user = current_user
#seller_items = current_user.seller_orders.map { |so| so.order_items.map { |oi| { item: oi.item } } }.flatten
#seller_items.to_a
end
end

Answer 1

A more complete answer, with less models, and named joins. You might want to "merge" the order and order_items tables, and remove the multiple if you're dealing with singular items for sale, e.g. cars, but for anything that is either bought in bulk or might be sold at the same time as something else you might want this layout:
generate your models:
rails g model User name:string
rails g model Item name:string
rails g model Order order_date:time status:string
rails g model OrderItem order:references item:references multiple:integer
modify create_order to add in the additional references:
def change
create_table :orders do |t|
t.time :order_date, index: true, null: false
t.string :status
t.references :buyer, index: true, null: false, foreign_key: {to_table: :users}
t.references :seller, index: true, null: false, foreign_key: {to_table: :users}
t.timestamps
end
migrate the models:
rake db:migrate
== 20201126090851 CreateUsers: migrating ======================================
-- create_table(:users)
-> 0.0036s
== 20201126090851 CreateUsers: migrated (0.0039s) =============================
== 20201126090858 CreateItems: migrating ======================================
-- create_table(:items)
-> 0.0030s
== 20201126090858 CreateItems: migrated (0.0032s) =============================
== 20201126091129 CreateOrders: migrating =====================================
-- create_table(:orders)
-> 0.0077s
== 20201126091129 CreateOrders: migrated (0.0081s) ============================
== 20201126091209 CreateOrderItems: migrating =================================
-- create_table(:order_items)
-> 0.0065s
== 20201126091209 CreateOrderItems: migrated (0.0067s) ========================
modify the models to add the joins:
app/models/user.rb
::::::::::::::
class User < ApplicationRecord
has_many :buyer_orders, class_name: "Order", foreign_key: :buyer, inverse_of: :buyer
has_many :seller_orders, class_name: "Order", foreign_key: :seller, inverse_of: :seller
end
::::::::::::::
app/models/item.rb
::::::::::::::
class Item < ApplicationRecord
has_many :order_items, inverse_of: :item
end
::::::::::::::
app/models/order.rb
::::::::::::::
class Order < ApplicationRecord
has_many :order_items, inverse_of: :order
belongs_to :seller, class_name: "User", inverse_of: :seller_orders
belongs_to :buyer, class_name: "User", inverse_of: :buyer_orders
end
::::::::::::::
app/models/order_item.rb
::::::::::::::
class OrderItem < ApplicationRecord
belongs_to :order, inverse_of: :order_items
belongs_to :item, inverse_of: :order_items
end
insert data:
User.create(name: "hello")
User.create(name: "again")
Item.create(name: "whatever")
Order.create(buyer: User.first, seller: User.last, order_date: Time.now())
OrderItem.create(item: Item.first, order: Order.first, multiple: 1)
test the output:
Check the status of the order:
2.7.0 :002 > Order.first
(0.5ms) SELECT sqlite_version(*)
Order Load (0.2ms) SELECT "orders".* FROM "orders" ORDER BY "orders"."id" ASC LIMIT ? [["LIMIT", 1]]
=> #<Order id: 1, order_date: "2000-01-01 09:26:22", status: nil, buyer_id: 1, seller_id: 2, created_at: "2020-11-26 09:26:22", updated_at: "2020-11-26 09:26:22">
2.7.0 :003 > Order.first.seller
Order Load (0.2ms) SELECT "orders".* FROM "orders" ORDER BY "orders"."id" ASC LIMIT ? [["LIMIT", 1]]
User Load (0.3ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 2], ["LIMIT", 1]]
=> #<User id: 2, name: "again", created_at: "2020-11-26 09:25:26", updated_at: "2020-11-26 09:25:26">
2.7.0 :004 > Order.first.buyer
Order Load (0.2ms) SELECT "orders".* FROM "orders" ORDER BY "orders"."id" ASC LIMIT ? [["LIMIT", 1]]
User Load (0.2ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 1], ["LIMIT", 1]]
=> #<User id: 1, name: "hello", created_at: "2020-11-26 09:25:18", updated_at: "2020-11-26 09:25:18">
Check the "buyer orders" of the first user:
2.7.0 :013 > User.first.buyer_orders
User Load (0.2ms) SELECT "users".* FROM "users" ORDER BY "users"."id" ASC LIMIT ? [["LIMIT", 1]]
Order Load (0.3ms) SELECT "orders".* FROM "orders" WHERE "orders"."buyer_id" = ? LIMIT ? [["buyer_id", 1], ["LIMIT", 11]]
=> #<ActiveRecord::Associations::CollectionProxy [#<Order id: 1, order_date: "2000-01-01 09:26:22", status: nil, buyer_id: 1, seller_id: 2, created_at: "2020-11-26 09:26:22", updated_at: "2020-11-26 09:26:22">]>
check the "seller orders" of the second user:
2.7.0 :014 > User.last.seller_orders
User Load (0.2ms) SELECT "users".* FROM "users" ORDER BY "users"."id" DESC LIMIT ? [["LIMIT", 1]]
Order Load (0.3ms) SELECT "orders".* FROM "orders" WHERE "orders"."seller_id" = ? LIMIT ? [["seller_id", 2], ["LIMIT", 11]]
=> #<ActiveRecord::Associations::CollectionProxy [#<Order id: 1, order_date: "2000-01-01 09:26:22", status: nil, buyer_id: 1, seller_id: 2, created_at: "2020-11-26 09:26:22", updated_at: "2020-11-26 09:26:22">]>
for peace of minds sake, check that the first user doesn't have any seller orders:
2.7.0 :015 > User.first.seller_orders
User Load (0.2ms) SELECT "users".* FROM "users" ORDER BY "users"."id" ASC LIMIT ? [["LIMIT", 1]]
Order Load (0.2ms) SELECT "orders".* FROM "orders" WHERE "orders"."seller_id" = ? LIMIT ? [["seller_id", 1], ["LIMIT", 11]]
=> #<ActiveRecord::Associations::CollectionProxy []>
2.7.0 :016 >
Controller
class UsersController < ApplicationController
def my_page
#user = current_user
#seller_orders = current_user.seller_orders
# remember that you might want to filter this in the future
# from_date = params[:from_date].present? ? params[:from_date] : Time.at(0)
# to_date = params[:to_date].present? ? params[:to_date] : Time.now()
# #seller_orders = #seller_orders.where(order_date: from_date..to_date)
end
end
view (I use haml)
%h1
= #user.username
Seller Orders
- #seller_orders.each do |so|
%table.seller_order{id: "seller_order_#{so.id}"}
%tr
%th Order Date:
%td= so.order_date
%tr
%th Buyer:
%td= so.buyer.username
%tr.spacer
%td{colspan: 2}
%tr
%th Item
%th Multiple
- so.order_items.each do |oi|
%tr
%td= oi.item.name
%td= oi.multiple
seller items
#seller_items = #seller_orders.map{|so| so.order_items.map{|oi| {multiple: oi.multiple, item: oi.item} }.flatten
or possibly (written from memory, not tested)
#seller_items = OrderItem.select("sum(order_items.multiple) as multiple, order_items.item_id as item_id").joins(:orders).joins(:buyer).where("users.id = ?", User.first.id).group("item_id")

Answer 2

You need something in the middle indeed - that's typicall called an "Order" in e-commerce with:
Link to User
Link to Item
but also maybe some more attributes:
Date of the sale
Status (cart/order/paid/delivered)
So indeed - you'll want an additional model there

Answer 3

class Seller < ApplicationRecord
belongs_to :user
has_many selling_items
has_many :items, through: :selling_items
end
class Buyer < ApplicationRecord
belongs_to :user
has_many bought_items
has_many :items, through: :bought_items
end
class Items < ApplicationRecord
end
class BoughtItem < ApplicationRecord
belongs_to :buyer
belongs_to :item
end
class SellingItem < ApplicationRecord
belongs_to :seller
belongs_to :item
end
class User < ApplicationRecord
end