How to sum properties of the objects within an array in Ruby
array = [1,2,3,4,5];
puts array.inject(0, &:+)

array.cash.inject(0, &:+) # (but this doesn't work)

array.map(&:cash).inject(0, &:+)

array.inject(0){|sum,e| sum += a.cash }

array.reduce(0) { |sum, obj| sum + obj.cash }

array.map(&:cash).inject(:+)