Date と Time に直前と直後の各曜日を取得するメソッドを追加

date_last_and_next.rb

class Date
  module Extender
    module LastAndNext
      ['sunday', 'monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday'].each_with_index do |weekday, index|
        define_method "last_#{weekday}" do
          return self if wday == index
          offset = wday - index
          self - (offset < 0 ? offset + 7 : offset)
        end
        define_method "next_#{weekday}" do
          return self if wday == index
          offset = wday - index
          self + (7 - (offset < 0 ? offset + 7 : offset))
        end
      end
    end
  end

  include Extender::LastAndNext
end

time_last_and_next.rb

class Time
  module Extender
    module LastAndNext
      ['sunday', 'monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday'].each_with_index do |weekday, index|
        define_method "last_#{weekday}" do
          return self if wday == index
          offset = wday - index
          self - (offset < 0 ? offset + 7 : offset) * 86400
        end
        define_method "next_#{weekday}" do
          return self if wday == index
          offset = wday - index
          self + (7 - (offset < 0 ? offset + 7 : offset)) * 86400
        end
      end
    end
  end

  include Extender::LastAndNext
end