On Tue, Feb 21, 2012 at 8:15 AM, LED <[email protected]> wrote:
> hi guys im playing with RoR with the environment of rails 3 ruby 1.9 i
> got stuck in
>
> nil can't be coerced into BigDecimal
>
> error
>
> i need to get the total cost of the products inside the cart i know
> where the problem is(i think) but i almost did every thing
> cart/show.html.rb
>
> <div class="cart_title" >Your Cart</div>
> <table>
> <% for item in @cart.line_items %>
> <tr>
> <td><%= item.quantity %>×</td>
> <td><%= item.product.title %></td>
> <td class="item_price" ><%= number_to_currency(item.total_price)
> %></td>
> </tr>
> <% end %>
> <tr class="total_line" >
> <td colspan="2" >Total</td>
> <td class="total_cell" ><%=
> number_to_currency(@cart.total_price) %></td>
> </tr>
> </table>
> <%= button_to 'Empty cart', @cart, :method => :delete,
> :confirm => 'Are you sure?' %>
>
> model/line_item.rb
>
> def total_price
> line_items.to_a.sum { |item| item.total_price }
> end
> model/cart.rb
>
> def total_price
> product.price * quantity
> end
> my second option is
>
> def total_price
> if product.price
> product.price * quantity
> else
> product.price = "0.0".to_d
>
This code is assigning a 0 to fixed price of a product
(most probably not what is intended). Probably simply
return a 0 (in BigDecimal) here.
> end
> end
> but still this wont work
>
Is there a business rule that each item must realistically have
a quantity and product (and that product must have a price) ?
In that case I suggest:
* add validations for the presence of these values
(presence of quantity and product on item
presence of price on product)
* write code like:
def total_price
if self.valid?
product.price * quantity
else
0.to_d
end
end
Another possible gotcha is that "item.product_id" is available
(e.g. from a select box), but item.product is not yet associated
(you may need to override the product_id= setter for that e.g.
def product_id=(product_id)
self.product = Product.find_by_id(product_id)
super
end
HTH,
Peter
--
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Peter Vandenabeele
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