class ConverterController < NSWindowController
  attr_writer :amount_field, :dollar_field, :rate_field

  def convert(sender)
    converter = Converter.new
    converter.source_currency_amount = dollar_field.floatValue
    converter.rate = rate_field.floatValue
    amount = converter.convert_currency

    amount_field.floatValue = amount
    rate_field.selectText(self)
  end
end

class Converter
  attr_accessor :source_currency_amount, :rate

  def convert_currency
    source_currency_amount * rate
  end
end