Ruby non-uniform hash array to csv

array_to_csv.rb

class Array
  def to_csv(filename="hash.csv")
    require 'csv'
    # Get all unique keys into an array:
    keys = self.flat_map(&:keys).uniq
    CSV.open(filename, "wb") do |csv|
      csv << keys
      self.each do |hash|
        # fetch values at keys location, inserting null if not found.
        csv << hash.values_at(*keys)
      end
    end
  end
end