Rubyクラス作成

ruby

class Car
  attr_reader :speed
  def initialize(speed)
    raise ArgumentError, 'speed < 0' if speed < 0
    @speed = speed
  end

  def time(distance)
    raise ArgumentError, 'distance < 0' if distance < 0
    return nil if @speed.zero?
    distance.to_f / @speed
  end
end

car = Car.new(50)
p car
p car.speed
p car.time(100) # => 2.0

car = Car.new(0)
p car.time(100) # => nil

begin
  Car.new(-1)
rescue ArgumentError => ex
  p ex
end