Solución con Method Missing

numeric_method_missing

1) Solución con método de clase
class Numeric
  CURRENCIES = {dollar: 1, yen: 0.013, euro: 1.292, rupee:  0.019} "Para versiones superiores a la 1.9 de Ruby"
  CURRENCIES = {:dollar => 1, :yen => 0.013, :euro => 1.292, :rupee => 0.019}

  
  def euros    
      self * CURRENCIES[:euro]
  end


  def in(currency)
    
    self / CURRENCIES[currency.to_sym]

  end
end



2) Solución con method missing
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class Numeric
  CURRENCIES = {dollar: 1, yen: 0.013, euro: 1.292, rupee:  0.019}
  
  def method_missing(method_id)
    singular_currency = method_id.to_s
    if CURRENCIES.has_key?(singular_currency.to_sym)
      self * CURRENCIES[singular_currency.to_sym]
    else
      super
    end
  end

  def in(currency)
    singular_currency = currency.to_s.gsub(/s$/, '')
    self / CURRENCIES[singular_currency.to_sym]
  end
end