Ruby Calulate Sum from Array

Question

I'm using rails to try and calculate the total of a specific column in my database. I'm using this at the moment:

@total = Product.sum (:cost)

Which works and returns the combined cost of everything in the table. What about if I'm trying to do that from data which is already in an array? For example:

@products = Product.where('date >= ? AND date <= ?', Date.today.beginning_of_month.to_datetime, Date.today.end_of_month.end_of_day.to_datetime)

Can you then do the same thing on that array of products?

Hope someone can help! Ta.

user229044 · Accepted Answer · 2013-01-07 17:54:02Z

4

You can simply append .sum to the resulting ActiveRecord object:

Product.where('date >= ? AND date <= ?',
 Date.today.beginning_of_month.to_datetime,
 Date.today.end_of_month.end_of_day.to_datetime).sum(:cost)

This will produce a query similar to

select sum(cost) from products where (date >= ... and date <= ...)

answered Jan 7, 2013 at 17:54

user229044♦

241k41 gold badges346 silver badges350 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

calabi Over a year ago

Oh fantastic! Can you then add this to it's own partial? Hope that's the correct terminology?

user1454117 · Accepted Answer · 2013-01-07 18:05:42Z

2

If you already have an instantiated array (not a relation object), you can use inject:

@total = @products.collect(&:cost).inject {|sum, cost| sum += cost }

meagar's answer works better if you have the relation though.

answered Jan 7, 2013 at 18:05

user1454117

Collectives™ on Stack Overflow

Ruby Calulate Sum from Array

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related