Module: Month::Serializer::ClassMethods

Defined in:
lib/month/serializer.rb

Instance Method Summary collapse

Instance Method Details

#dump(month) ⇒ Object 



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# File 'lib/month/serializer.rb', line 65

def dump(month)
  raise_dump_error(month) unless month.is_a?(self)
  month.to_i
end

#load(month_as_integer) ⇒ Object 



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# File 'lib/month/serializer.rb', line 13

def load(month_as_integer)
  raise_load_error(month_as_integer) unless month_as_integer.is_a?(Integer)
  year, number = month_as_integer.divmod(12)
  # A zero month actually points to December of the previous year,
  #   because when dividing by 12, possible remainders are 0 - 11
  #   and we need months 1 - 12
  #
  # NOTE ON ZERO:
  #
  # There is no Year Zero in the anno domini system.
  # See: https://en.wikipedia.org/wiki/Year_zero
  #
  # But ISO 8601:2004 does have a year zero, and it coincides with Gregorian year 1 BC.
  # See: https://en.wikipedia.org/wiki/ISO_8601
  #
  # And what about Ruby?
  #
  # >> Date.new(0, 1, 1)
  # => #<Date: 0000-01-01 ((1721058j,0s,0n),+0s,2299161j)>
  # >> Date.new(0, 1, 1) << 1
  # => #<Date: -0001-12-01 ((1721027j,0s,0n),+0s,2299161j)>
  # >> Date.new(0, 1, 1) >> 12
  # => #<Date: 0001-01-01 ((1721424j,0s,0n),+0s,2299161j)>
  # >> Date.new(2018, 1, 1) >> 12
  # => #<Date: 2019-01-01 ((2458485j,0s,0n),+0s,2299161j)>
  #
  # We want a line of integers that represent months that are unbroken
  #   steps of distance 1, so we have to have a Month 0
  #
  # Month -24 is December, Year -3  # -24.divmod(12) => [-2, 0]   # year -= 1, number = 12
  # Month -23 is January, Year -2   # -23.divmod(12) => [-2, 1]   # no mod
  # Month -12 is December, Year -2  # -12.divmod(12) => [-1, 0]   # year -= 1, number = 12
  # Month -11 is January, Year -1   # -11.divmod(12) => [-1, 1]   # no mod
  # Month -10 is February, Year -1  # -10.divmod(12) => [-1, 2]   # no mod
  # Month -2 is October, Year -1    # -2.divmod(12) => [-1, 10]   # no mod
  # Month -1 is November, Year -1   # -1.divmod(12) => [-1, 11]   # no mod
  # Month 0 is December, Year -1    # 0.divmod(12) => [0, 0]      # year -= 1, number = 12
  # Month 1 is January, Year 0      # 1.divmod(12) => [0, 1]      # no mod
  # Month 2 is February, Year 0     # 2.divmod(12) => [0, 2]      # no mod
  # Month 11 is November, Year 0    # 11.divmod(12) => [0, 11]    # no mod
  # Month 12 is December, Year 0    # 12.divmod(12) => [1, 0]     # year -= 1, number = 12
  # Month 13 is January, Year 1     # 13.divmod(12) => [1, 1]     # no mod
  # Month 23 is November, Year 1    # 23.divmod(12) => [1, 11]    # no mod
  # Month 24 is December, Year 1    # 24.divmod(12) => [2, 0]     # year -= 1, number = 12
  # Month 25 is January, Year 2     # 25.divmod(12) => [2, 1]     # no mod
  if number.zero?
    number = 12
    year -= 1
  end
  self.new(year, number)
end