在String和Classname之间转换 [英] Cast between String and Classname

问题描述

我有一个字符串，包含一个类名。它例如是包含Article的字符串。那个字符串来自params []。我应该如何处理这个字符串，就像它是一个类名？例如，我想做：

  Article.all 
    
解决方案
此解决方案优于 eval ，因为您正在评估可能由用户操纵并可能包含有害操作的 params 散列。作为一般规则：不要直接评估用户输入，这是一个很大的安全漏洞。 
 补丁for String class 
 class String 
 def to_class 
 klass = Kernel.const_get（self）
 klass.is_a？（Class）？ klass：nil 
 rescue NameError 
 nil 
 end 
 end 
 
＃示例
Fixnum.to_class＃=> Fixnum 
Something.to_class＃=> nil 
  
 更新 - 适用于命名空间的更好的版本： > 
 
 
 ＃String类的猴子补丁
 class String 
 def to_class 
 chain = self.split： ：
 klass = Kernel 
 chain.each do | klass_string | 
 klass = klass.const_get klass_string 
 end 
 klass.is_a？（Class）？ klass：nil 
 rescue NameError 
 nil 
 end 
 end 
  
 
I have a string, containing an Class name. It is, for example, a string containing "Article". That string came up from the params[]. What should I do to work with this string as if it was a class name? For instance, I want to do:
Article.all
and so on.

Any idea?
解决方案
This solution is better than eval as you are evaluating params hash that might be manipulated by the user and could contain harmful actions. As a general rule: Never evaluate user input directly, that's a big security hole.
# Monkey patch for String class
    class String
      def to_class
        klass = Kernel.const_get(self)
        klass.is_a?(Class) ? klass : nil
      rescue NameError
        nil
      end
    end

# Examples
"Fixnum".to_class #=> Fixnum
"Something".to_class #=> nil
Update - a better version that works with namespaces:
 # Monkey patch for String class
    class String
      def to_class
        chain = self.split "::"
        klass = Kernel
        chain.each do |klass_string|
          klass = klass.const_get klass_string
        end
        klass.is_a?(Class) ? klass : nil
      rescue NameError
        nil
      end
    end


                        
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