How to save ids to users columns - ruby-on-rails

Question

So I've built a system of products and a shopping cart in my rails app. The goal I have is to add ids of the saved products from a cart to the user model. So in my cart view page there is a list of all added products in a cart and I want to add a save button which will save those products by their ids to the columns in users table. As an example, if current_user ads three products in the cart with ids 1,2,3 and clicks on "Save" button in a cart, I want to be able to save those three ids by integers to the three columns: product_one, product_two, product_three of the current_user.
So far these are my models:
class Item < ActiveRecord::Base
has_one :cart
end
class User < ActiveRecord::Base
has_one :cart
has_many :items, through: :cart
end
class Cart < ActiveRecord::Base
belongs_to :user
belongs_to :item
validates_uniqueness_of :user, scope: :item
end
My controllers:
class ItemsController < ApplicationController
before_action :set_item, only: [:show, :edit, :update, :destroy]
respond_to :html, :json, :js
def index
#items = Item.where(availability: true)
end
def show
end
def new
#item = Item.new
end
def edit
end
def create
#item = Item.new(item_params)
#item.save
respond_with(#item)
end
def update
#item.update(item_params)
flash[:notice] = 'Item was successfully updated.'
respond_with(#item)
end
def destroy
#item.destroy
redirect_to items_url, notice: 'Item was successfully destroyed.'
end
private
def set_item
#item = Item.find(params[:id])
end
def item_params
params.require(:item).permit(:name, :description, :availability)
end
end
my cart controller:
class CartController < ApplicationController
before_action :authenticate_user!, except: [:index]
def add
id = params[:id]
if session[:cart] then
cart = session[:cart]
else
session[:cart] = {}
cart = session[:cart]
end
if cart[id] then
cart[id] = cart[id] + 1
else
cart[id] = 1
end
redirect_to :action => :index
end
def clearCart
session[:cart] = nil
redirect_to :action => :index
end
def index
if session[:cart] then
#cart = session[:cart]
else
#cart = {}
end
end
end
And I'm using Devise for authentication..

Answer 1

I think you may have misunderstood the Rails relations and how to use them. As the methods to define relation are pretty much literal, take a good look at your models and 'read' them.
An item has one cart
A cart belongs to a item
Does it make sense that an item has one cart? Wouldn't make more sense to a cart to have an item, or several?
A cart has one or more items
One item belongs to a cart
And then, you just translate that into rails methods:
class User < ActiveRecord::Base
has_one :cart
end
class Cart < ActiveRecord::Base
belongs_to :user #carts table must have a user_id field
has_many :items
end
class Item < ActiveRecord::Base
belongs_to :cart #items table must have a cart_id field
end
Now, let's return to the literals. So, if I have a user and want to know what items he has in a cart, what do I do?
I know a user has one cart
I know that a cart has one or more items
So, to recover the items that a user has in a cart:
user.cart.items
And answering your original question, how to save the items to a user? You don't need to. If the user has a cart and this cart has items then, automatically, user has items (accessing them through the cart, as stated above).