如何在“case when”中捕获Errno :: ECONNRESET类？ [英] How to catch Errno::ECONNRESET class in "case when"?

问题描述

我的应用程序（Ruby 1.9.2）可能引发不同的异常，包括网络连接中断。我 rescue Exception => e ，然后执行 case / when 以不同的方式处理它们，但是几个错误通过我的案例直到 else 。

  rescue Exception => e 
p e.class 
 case e.class 
当Errno :: ECONNRESET 
p 1 
当Errno :: ECONNRESET，Errno :: ECONNABORTED，Errno :: ETIMEDOUT 
p 2 
 else 
p 3 
 end 
 end 
  

打印：

  Errno :: ECONNRESET 
 3 
  / pre> 
 
解决方案
这是因为 === 在类上工作 
 
 
 
 案例 a href =http://ruby-doc.org/core/classes/Object.html#M000345 =noreferrer>内部调用  === 方法对您正在评估的对象。如果你想测试 e 类，你只需要测试 e 而不是 e。类。那就是因为，在Class  case时，因为 e.class 将落入中，因为e.class是一个Class。 
  rescue Exception =>当Errno :: ECONNRESET，Errno :: ECONNABORTED，Errno :: ETIMEDOUT 
p 2 
时，e 
 case e 
当Errno :: ECONNRESET 
p 1 
 
p 3 
 end 
 end 
  
是的，Ruby可以有奇怪语义有时
 
My application (Ruby 1.9.2) may raise different exceptions, including net-connection breaks. I rescue Exception => e, then do case/when to handle them in defferent ways, but several errors go through my cases straight to else.
rescue Exception => e
    p e.class
    case e.class
        when Errno::ECONNRESET
            p 1
        when Errno::ECONNRESET,Errno::ECONNABORTED,Errno::ETIMEDOUT
            p 2
        else
            p 3
    end
end
Prints:
Errno::ECONNRESET
3

解决方案
This is because of how the === operator works on the class Class

The case statement internally calls the === method on the object you are evaluating against. If you want to test for e class, you just test against e, not e.class. That's because e.class would fall into the when Class case, because, well, e.class is a Class.
rescue Exception => e
    case e
        when Errno::ECONNRESET
            p 1
        when Errno::ECONNRESET,Errno::ECONNABORTED,Errno::ETIMEDOUT
            p 2
        else
            p 3
    end
end
Yeah, Ruby can have weird semantics sometimes

                        
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