Crunch: sum, sort_by, min_by

sum — add up a field with a block

sum totals a collection of numbers directly, but its real power shows up with a block: give it a block and it sums WHATEVER the block returns for each item, without a separate map step first:

bookings = [{ price_cents: 2500 }, { price_cents: 3000 }, { price_cents: 2000 }]
total_cents = bookings.sum { |b| b[:price_cents] }
# 7500

Read bookings.sum { |b| b[:price_cents] } as "for each booking, take its price_cents, and add all of those together."