title: How to save ids to users columns
body: <p>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.</p>
  
  <p>So far these are my models:</p>
  
  <pre><code>class Item &lt; ActiveRecord::Base
      has_one :cart
  end
  
  class User &lt; ActiveRecord::Base
  
    has_one :cart
    has_many :items, through: :cart 
  end
  
  class Cart &lt; ActiveRecord::Base
  
    belongs_to :user
    belongs_to :item
  
    validates_uniqueness_of :user, scope: :item
  end
  </code></pre>
  
  <p>My controllers:</p>
  
  <pre><code>class ItemsController &lt; 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
  </code></pre>
  
  <p>my cart controller:</p>
  
  <pre><code>class CartController &lt; 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 =&gt; :index
    end
  
  
    def clearCart
      session[:cart] = nil
      redirect_to :action =&gt; :index
    end
  
  
  
  
  
  
    def index
      if session[:cart] then
        @cart = session[:cart]
      else
        @cart = {}
      end
  
    end
  end
  </code></pre>
  
  <p>And I'm using Devise for authentication..</p>