CODEWITHSUNDEEP
ruby-on-railsrubyruby-on-rails-3
Tim K.
Tim K.

Reputation: 170

How do I find the sum of donations per month for 24 months?

Having pulled donations from the past two years, I'm trying to derive the sum of those donations per month (a total of 24 sums), storing the keys (each month) and the values (the sum of donations for each month) in an array of hashes.

Here's what I've got so far:

@donations = Gift.between(Date.today - 2.years, Date.today, :field => gift_date)

@donations.each do |donation|
   #logic here that puts gift_amount into the right month (of the 24 months) 
   # and adds it to the previous balance for that month, ending up with 24 keys 
   # and sum values.
end

How can I do this in Ruby/Rails?

Upvotes: 2

Views: 154

Answers (2)

ichigolas
ichigolas

Reputation: 7725

Continuing where @mbratch left off:

donations = Gift.where(:date => (Date.today - 2.years)..Date.today)
Hash[donations.group_by { |d| [d.date.year, d.date.month] }
.map do |year_month, donations|
  [year_month, donations.map(&:amount).reduce(:+)]
end]

Upvotes: 2

lurker
lurker

Reputation: 58244

donation_hash = Hash.new(0)

Gift.where(:gift_date => (Date.today - 2.years)..Date.today).each do |donation|
  donation_hash[[donation.gift_date.month, donation.gift_date.year]] += donation.amount
end

This will create a hash with keys of [month, year] and value of total amount donated for that month/year. There are probably a few other suitable ways to create a key which meets the need of your application.

Upvotes: 0

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