Rails session variable (shopping cart) - ruby-on-rails

Question

I'm trying to save the items the customer can add to my shopping cart in a session variable.
Below is my index method in the cart controller. The ID of the item is saved in #idtemp. Next I create a new array session[:content]. Then I find the item with the ID saved in #idtemp and return it as an array, which is used in the view to display the table. The problem is, everytime an item is added and the index function is called, session[:contenc] is set to [], deleting the cart, which means that a newly added item overwrites the last one.
Now I want this fixed so that a newly added item is added to the array without overwriting the last one, but I dont know how. I tried to initialize the session variable outside of index but that didnt work somehow. I know this is piss easy but I am pretty exhausted and cant figure it out.
def index
#idtemp = session[:cart]
session[:content] = []
session[:content] = session[:content] << (Artikel.find([#idtemp]))
#cart = session[:content]
end
-----view:
<% #cart.each do |id,quantity| %>
...
...

Answer 1

If i was you i would store the cart and its contents in the database. Then all the session has to do is to remember either the cart id, or the id of the user, if they're logged in (once you've got the user you can get the cart). I'd set it up something like this (which you can adjust for your own schema - Artikle or whatever instead of Product)
class Cart
belongs_to :user
has_many :cart_products
class CartProduct
belongs_to :cart
belongs_to :product
#extra field - quantity
When the page loads, look to see if you have session[:cart_id]. if you do, you can load the cart, and its associated products if need be. If not, then create a cart object and set session[:cart_id] to that.
If you have a logged in user (ie session[:user_id] or somesuch) then you can set current_user to that user, and set their cart.
I would manage this via some protected methods in ApplicationHelper
#in application.rb
def current_user
if #current_user
return #current_user
elsif session[:user_id] && user = User.where(:id => session[:user_id]).first
#current_user = user
return #current_user
end
end
#there's a bit of repetition in here but it should give you the idea
def current_cart
unless #current_cart
if current_user
cart = current_user.cart || Cart.create(:user => current_user)
#current_cart = cart
elsif session[:cart_id]
#current_cart = Cart.where(:id => session[:cart_id]).first || Cart.create
else
#current_cart = Cart.create
end
end
return #current_cart
end
Now, whenever you want to refer to the current user, or the current cart, in your controller and view code, just say current_user or current_cart. The instance variables inside each method mean that if it's been set once in this request then it won't use the logic again - it will just use the one it already saved in the instance variable.

Answer 2

Ok, adapting your existing system, i would do it like this. We'll have one session variable, which is a hash storing the ids of Artikels and the quantity of each, with this structure: session[:cart] = {123 => 1, 456 => 2} where 123 and 456 are Artikel ids.
def add
session[:cart] ||= {}
session[:cart][params[:id]] ||= 0
session[:cart][params[:id]] += 1
end
def index
session[:cart] ||= {}
end
now in your view you can say
<% session[:cart].each do |artikel_id, quantity| %>
<% artikel = Artikel.where(:id => artikel_id).first %>
...

Answer 3

Here is what i dont understand:
def index
#idtemp = session[:cart] # #idtemp is now an ID e.g. '1'
session[:inhalt] = [] # session[:inhalt] is now an empty array []
addedarticle = Artikel.find(#idtemp) # addedarticle is an article e.g.:{ID=>'1',title=>'Mouse'}
session[:inhalt].concat([addedarticle]) # session[:inhalt] is now [{...}] where {...} = article
#cart = session[:inhalt] # #cart = [{...}]
end
This works. An item is added to the cart and #cart is an array containing this item, it can now be used in the view. The only thing that has to be done now is to make sure that the next added item wont override the old ond. You said i can simply replace session[:inhalt] = [] with session[:inhalt] ||= [],
however, doing this leads to an error:
NoMethodError in Cart#index
undefined method `title' for "#":String
<% #cart.each do |id| %>
<tr>
<td><%= image_tag id.Image_URL %></td>
<td>
<div class="title"><%= id.title %></div>
<br>
It seems to me that #cart is not properly "filled". Its supposed to be an array of articles (=hashes) e.g. [{id => 1, title ='mouse'}, {id => 2, title = 'whatever'}], so i can iterate over it with the each do method and display them. But according to the error it is trying to extract the title from a string. What could be the cause of that?
If I can fix this, I am done with the task. Btw, thanks for helping me out so far :)