大致是这样的: class Vehicle
VEHICLES = {}
def self.register_vehicle name
VEHICLES[name] = self
end
def self.vehicle_from_name name
VEHICLES[name].new
end
end
class Bike < Vehicle
register_vehicle 'mountain bike'
end
class Car < Vehicle
register_vehicle 'ferrari'
end > Vehicle.vehicle_from_name 'ferrari'
=> #<Car:0x7f5780840448>
> Vehicle.vehicle_from_name 'mountain bike'
=> #<Bike:0x7f5780839198> 通过所有子类: require 'require_all'
require_rel 'vehicles'
我也不会调用两个多(is_a?和kind_of?是同一方法的别名),但如果你想看到更多的可能性,将注意力转移到#class方法:
A = Class.new
B = Class.new A
a, b = A.new, B.new
b.class < A # true - means that b.class is a subclass of A
a.class < B # false - means that a.class is not a subclass of A
# Another possibility: Use #ancestors
b.class.ancestors.include? A # true - means that b.class has A among its ancestors
a.class.ancestors.include? B # false - means that B is not an ancestor of a.class