动态创建没有名称空间的类 [英] dynamically create a class without a namespace

问题描述

我正在尝试使用eval方法动态创建一个类.除了一个小问题，它工作正常.如我的代码所示，我正在BrowserFactory类内创建Browser类.当我这样做时，Browser类具有添加的BrowserFactory命名空间.无论如何，在没有附加BrowserFactory命名空间的情况下，是否可以通过字符串评估Browser类?

I am trying to dynamically create a class using the eval method. It is working fine except for one small problem. As my code shows I am creating the Browser class inside the BrowserFactory class. When I do this the Browser class has an added namespace of BrowserFactory. Is there anyway to evaluate the Browser class from a string without the BrowserFactory namespace being attached?

class BrowserFactory
  def self.create_browser(browser)
    super_class = nil
    case browser
    when 'IE'
      require 'watir'
      super_class = 'Watir::IE'
    when 'celerity'
      require 'celerity'
      super_class = 'Celerity::Browser'
    end

    raise StandardError.new("Browser '#{browser}' is not currentlys supported") if super_class.nil?

    eval <<EOS
class Browser < #{super_class}
include Singleton
include BrowserModification
end
EOS

    return Browser.instance
  end

end

推荐答案

定义浏览器(或:: Browser，直接回答您的问题)将阻止您多次致电工厂.

Defining Browser (or ::Browser, to directly answer your question) will prevent you from calling your factory more than once.

我建议使用匿名类.不需要eval，顺便说一句，如果需要，您可以将类方法定义为to_s:

I would recommend to use an anonymous class. No need for eval, btw, and you can define the class method to_s if you want to:

class BrowserFactory
  def self.create_browser(browser)
    super_class = case browser
    when 'IE'
      require 'watir'
      Watir::IE
    when 'celerity'
      require 'celerity'
      Celerity::Browser
    else
      raise StandardError.new("Browser '#{browser}' is not currentlys supported")
    end

    klass = Class.new(super_class) do
      include Singleton
      include BrowserModification
      def self.to_s
        "Modified#{superclass}"
      end
    end
    klass.instance
  end
end

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