Ruby：如何在不创建新实例的情况下检查实例方法的参数？

Question

在Ruby 1.9.2中，您可以使用方法（：symbol）检查任何方法的参数。如何在不创建新车的情况下检查Car＃initialize方法？

class Car
  def initialize(fuel_type, passenger_capacity, door = 3)
    puts "TODO"
  end
end

Car.new(nil,nil).method(:initialize).parameters
  #=> [[:req, :fuel_type], [:req, :passenger_capacity], [:opt, :door]]

Instance_eval无效：

Car.instance_eval { |x| p x.method(:initialize).parameters } #=> [[:rest]]

Answer 1

Car.instance_method(:initialize).parameters
# => [[:req, :fuel_type], [:req, :passenger_capacity], [:opt, :door]]