Printing running total in do loop

Ok, so I'm really new to Ruby and Rails. I'm trying to create a home
budget app, and I'm having some difficulties getting a running total
working. I have the following code in my model:
def running_total
      @total = 0.0
      @transactions = Transaction.find(:all, :conditions =>
["category_id=?", category.id])
      @transactions.each do |transaction|
        @total += transaction.amount.to_f
        return @total
      end
end

What happens is I get the first expense amount, but it repeats for
every row in the table.
Date Payee Amount Total
2008-12-03 test 17.98 17.98
2008-12-03 test 0.57 17.98
2008-12-03 test 19.04 17.98

This is my first app with Rails, so I'm not sure everything is in the
right place. I created a Ruby script that contains the following:
result = dbh.query("select amount from transactions where category_id
= 6")
test = 0.0
result.each do |row|
   test += row[0].to_f
   puts test
end

The script works like it should, it increments the total after every
pass. Not sure what I'm doing wrong with the Rails portion. Any help
would be great. If you need me to post any more detail, just let me
know.

denied39 wrote:

 Ok, so I'm really new to Ruby and Rails. I'm trying to create a home
budget app, and I'm having some difficulties getting a running total
working. I have the following code in my model:
def running_total
@total = 0.0
@transactions = Transaction.find(:all, :conditions =>
["category_id=?", category.id])
@transactions.each do |transaction|
@total += transaction.amount.to_f
return @total
end
end
What happens is I get the first expense amount, but it repeats for
every row in the table.
Date Payee Amount Total
2008-12-03 test 17.98 17.98
2008-12-03 test 0.57 17.98
2008-12-03 test 19.04 17.98
This is my first app with Rails, so I'm not sure everything is in the
right place. I created a Ruby script that contains the following:
result = dbh.query("select amount from transactions where category_id
= 6")
test = 0.0
result.each do |row|
test += row[0].to_f
puts test
end
The script works like it should, it increments the total after every
pass. Not sure what I'm doing wrong with the Rails portion. Any help
would be great. If you need me to post any more detail, just let me
know.

Your loop
ends with the “return @total” instead of totaling the transactions.
Move the return down to after the end and I think you will be happier.

Norm

Ok, I moved the return @total after the "end", and now I get the
following:

2008-12-03 test 17.98 191.72
2008-12-03 test 0.57 191.72
2008-12-03 test 19.04 191.72

(there are more rows, I just cut it to three for the example)
So, the total works, but it doesn't increment the total after every
row. I seem to get either the first amount, or the sum.

The reason the total is the same on every row rather than being a running total is that your code calculates the total once for all all transactions of the given category. If you want a running total you will have to have an array @totals where the first element is the first transaction, the second is that plus the second transaction, the third is that plus the third transaction and so on, then display this in the view.
Colin

@Aldo - I tried the inject method, and it looks like it might work,
but I get an undefined method "amount" error. It lists the total of
the first two amount in the error, so it is adding, but somewhere it
is failing in the code. I'm not sure if I have things in the right
model or not, so that could be the issue. The customer model you were
referring to is actually a category model. I tried to move the code
from the transaction model to the category model like you described,
but that also failed to work. Which could very well be me not having
the view looking in the right place.

@Colin - I understand what you mean about the array, but I thought the
@total =+ transactions.amount.to_f would increment the total for each
row. Again, this could be my novice understanding of the web (and
Rails) way of programming. Up to this point, I've only ever written
command line scripts for Perl. I'll definitely give the added array a
try and see if I can make that work.

As I struggle through this, I wonder if I'm just really over-thinking
this problem. Do I really need a running total, or would a final sum
be adequate? I'm going to try the solutions everyone proposed before I
scrap the running total idea.

Thanks for you help so far. I'll post my progress later this evening.