Nil being coerced to float


#1

I was doing this:

 @line_items = LineItems.find_all_by_invoice_id(params[:id])
 @payments = Payments.find_all_by_invoice_id(params[:id])

@total = @line_items.sum{ |item| item.cost }
@payment_total = @payments.sum{ |payment| payment.value }

@balance = @total - @payment_total

But when no payments had been made it was coming up with an error when
trying to sum nil, so I did this:

 begin
      @payment_total = @payments.sum{ |payment| payment.value }
 rescue
      @payment_total = 0
 end

So, when the sum failed it returned @payment_total as zero. Now, SURELY,
there’s a better way to do this? I’m sure it’s obvious when you know
how. Please, enlighten me.


#2

All you need to do to your original code is add a condition to make
sure @payments is not null:
@payment_total = @payments.sum{ |payment| payment.value } unless
@payments.nil?

Or can payment.value be nil for some payments but not others? Inject
could help in that case:
@payment_totals = @payments.inject(0) { |sum, p| sum + p.value unless
p.value.nil? }

Before running either one of these, you can initialize both @total and
@payment_total to zero:
@total, @payment_total = 0, 0

Hope that helps.

PS: Wonder if you need all of these to be @instance_variables ?

On Apr 1, 10:16 am, Tom H. removed_email_address@domain.invalid


#3

On Wed, Apr 1, 2009 at 9:16 AM, Tom H.
removed_email_address@domain.invalid wrote:

I was doing this:

@line_items = LineItems.find_all_by_invoice_id(params[:id])
@payments = Payments.find_all_by_invoice_id(params[:id])

@total = @line_items.sum{ |item| item.cost }
@payment_total = @payments.sum{ |payment| payment.value }

You can do

@payment_total = @payments.sum{ |payment| payment.value } if @payments

or

@payment_total = @payments.sum{ |payment| payment.value } rescue 0

or

@payment_total = @payments ? @payments.sum{ |payment| payment.value } :
0

end

So, when the sum failed it returned @payment_total as zero. Now, SURELY,
there’s a better way to do this? I’m sure it’s obvious when you know
how. Please, enlighten me.


Greg D.
http://destiney.com/


#4

Thanks Guys, that’s much more Ruby like code!