strategy_pattern.rb

class Rate
  attr_accessor :credit_card, :value,

  def self.calculate(credit_card, value)
    new(credit_card, value).calculate
  end

  def initialize(credit_card, value)
    @credit_card = credit_card
    @value = value.to_i
  end

  def calculate
    rate = "blank"

    case credit_card
    when 'master_card'
      rate = calculate_rate(0.1)
    when 'visa'
      rate = calculate_rate(0.2)
    when 'elo'
      rate = calculate_rate(0.5)
    else
      rate = 'Credit Card brand unknow'
    end

    puts "The rate of #{credit_card} is #{rate}"
  end

  private def calculate_rate(credit_rate)
    value - (value * credit_rate)
  end
end