Question

我有一个对象Animal，当我传入一个类型时，我选择其中一个子类并在那里实例化它。如下所示：

class Museum::Animal

    def initialize type

        case type
        when "cat"
           CatAnimal.new
        when "dog"
           DogAnimal.new
        end
    end
end

但是Rails给了我错误：预期..file路径../animal.rb来定义Animal

有问题的文件位于lib / museum / animal.rb

Answer 1

module Barn
  # parent class
  class Animal
     def say
       'default'
     end
  end

  # inheritance for cat
  class Cat < Animal
    def say
      "meow"
    end
  end

  #inheritance for dog
  class Dog < Animal
  end

  # Factory to get by "type"
  def self.get type
    case type
    when :dog
      Dog.new
    when :cat
      Cat.new
    end 
  end 
end

并将其存储为lib / barn.rb。然后你可以这样做：

require 'barn'

c = Barn.get :cat
 => #<Barn::Cat:0x0000010719ffe8> 
c.say
 => "meow" 

d = Barn.get :dog
 => #<Barn::Dog:0x00000107190408> 
d.say
 => "default"

Rails很生气我正在从父类中实例化一个孩子

1 个答案: