デザインパターンbuilder

builderパターンです
作成過程が同じで異なる表現形式の結果を得るためのパターン

class SaltWater

  attr_accessor :water, :salt

  def initialize(water, salt)

    @water = water

    @salt = salt

  end

end

class SaltWaterBuilder

  def initialize

    @salt_water = SaltWater.new(0,0)

  end

  def add_solute(salt_amount)

    @salt_water.salt += salt_amount

  end

  def add_solvent(water_amount)

    @salt_water.water += water_amount

  end

  def abandon_solution(salt_water_amount)

    @salt_water.salt *= 1 - salt_water_amount / (@salt_water.salt + @salt_water.water)

    @salt_water.water *= 1 - salt_water_amount / (@salt_water.salt + @salt_water.water)

  end

  def result

    @salt_water

  end

end

class Director

  def initialize(builder)

    @builder = builder

  end

  def constract

    @builder.add_solvent(100)

    @builder.add_solute(40)

    @builder.abandon_solution(70)

    @builder.add_solvent(100)

    @builder.add_solute(15)

  end

end
b = SaltWaterBuilder.new

d = Director.new(b)

d.constract

p b.result

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