# Summing problem

I am trying to show the total price of an order, but i keep getting
this problem;
wrong number of arguments (1 for 2)

On this method, in the order.rb model;

def total
order_items.sum { |item| item.total }
end

An order consists of several order_items via a has_many relationship,
the total method found in order_items.rb looks like this;
def total
self.quantity * self.product.price
end

And as you can guess, an order_item refers to a product.

I am simply calling this in the view;
for orders in @orders do
order.total
end

I just cant seem to get it working, help is greatly appreciated.

AR::Calculations have a sum() method, so Iâ€™d guess itâ€™s not using
Enumerable#sum.

Try :

order_items.inject { |total, item| total += item.total }

On 8/24/07, Glimjaur [email protected] wrote:

order.total
end

I just cant seem to get it working, help is greatly appreciated.

â€“
Cheers!

On Aug 24, 2007, at 7:26 AM, Pratik wrote:

end
I am simply calling this in the view;

order_items.inject { |total, item| total += item.total }

â€“
Cheers!

Pratik is likely right, but I wanted to correct his use of #inject in
this case:

order_items.inject(0.0) { |total, item| total + item.total }

Without a starting point (0.0), the initial value is taken as the
first element which is an Item not a number. Also, it is unnecessary
to use += since the local value of total isnâ€™t whatâ€™s important, but
the value of the block (i.e., the last expression value) so just
using + is sufficient.

As for â€śwhyâ€ť the order_items.sum isnâ€™t working, your definition of
#total is not a database column so the total canâ€™t be obtained from
the generated SQL directly (at least not without duplicating the
definition of total and that wouldnâ€™t be very DRY, would it?).

-Rob