Undefined local variable or method to_a in Rails?

Question

This function...

class Invoice < ActiveRecord::Base

  def self.open_subtotal
    sum{ |i| i.open_amount / (1.00 + i.tax_rate / 100.00) }
  end

end

...gives me an error in Rails 4.0.2:

DEPRECATION WARNING: Calling #sum with a block is deprecated and will be removed in Rails 4.1. If you want to perform sum calculation over the array of elements, use to_a.sum(&block).

When I add to_a before sum I get an undefined local variable or method to_a error.

What is the correct way to write this?

And why are you keeping money in floats? http://stackoverflow.com/questions/3730019/why-not-use-double-or-float-to-represent-currency — Mike Szyndel, Jul 01 '14 at 13:35
@MichalSzyndel: Actually all my money values are saved as `decimals` in the database. Will my code above mess that up? — Tintin81, Jul 01 '14 at 13:42
Every time you write `0.4` it's a float in Ruby, so yes, it will mess up. If you have to multiply something by tax value use `BigDecimal.new` for instantiating tax rate. — Mike Szyndel, Jul 01 '14 at 13:45

score 3 · Answer 1 · answered Jul 01 '14 at 13:35

Apparently this is the way to do it nowadays...

select('sum(invoices.open_amount / (1.00 + invoices.tax_rate / 100.00) as open_subtotal')[0][:open_subtotal]

This does the calculations at the database level, appending as a new attribute open_subtotal which you then retrieve from the first instance of the select.

Taken from this blog.. http://stim371.github.io/blog/2014/02/12/deprecating-blocks-on-activerecord-count-and-sum/

Stefan · Accepted Answer · 2014-07-01T13:45:47.537

1

This would work:

def self.open_subtotal
  all.to_a.sum { |i| i.open_amount / (1.00 + i.tax_rate / 100.00) }
end

But you can probably sum it in SQL (assuming open_amount and tax_rate are fields in your invoices table):

def self.open_subtotal
  sum("open_amount / (1 + tax_rate / 100)")
end

edited Jul 01 '14 at 13:45

answered Jul 01 '14 at 13:33

Stefan

109,145
14
143
218

Undefined local variable or method to_a in Rails?

2 Answers2