SystemExit是一种特殊的异常？

问题描述

如何 c c> c c c c （它使用什么标准？）

But how does the rescue ignore SystemExit? (What criteria does it use?)

推荐答案

当你写 rescue 没有一个或多个课程，作为写作：

When you write rescue without one or more classes, it is the same as writing:

begin
  ...
rescue StandardError => e
  ...
end

有异常不继承 StandardError 。 SystemExit 是其中之一，因此没有被捕获。这是Ruby 1.9.2中的层次结构的一个子集，您可以：

There are Exceptions that do not inherit from StandardError, however. SystemExit is one of these, and so it is not captured. Here is a subset of the hierarchy in Ruby 1.9.2, which you can find out yourself:

BasicObject
  Exception
    NoMemoryError
    ScriptError
      LoadError
        Gem::LoadError
      NotImplementedError
      SyntaxError
    SecurityError
    SignalException
      Interrupt
    StandardError
      ArgumentError
      EncodingError
        Encoding::CompatibilityError
        Encoding::ConverterNotFoundError
        Encoding::InvalidByteSequenceError
        Encoding::UndefinedConversionError
      FiberError
      IOError
        EOFError
      IndexError
        KeyError
        StopIteration
      LocalJumpError
      NameError
        NoMethodError
      RangeError
        FloatDomainError
      RegexpError
      RuntimeError
      SystemCallError
      ThreadError
      TypeError
      ZeroDivisionError
    SystemExit
    SystemStackError
    fatal

您可以通过以下方式捕获只是 SystemExit ：

You can thus capture just SystemExit with:

begin
  ...
rescue SystemExit => e
  ...
end

...或者您可以选择捕获每个异常，包括 SystemExit 与：

...or you can choose to capture every exception, including SystemExit with:

begin
  ...
rescue Exception => e
  ...
end

自己尝试：

begin
  exit 42
  puts "No no no!"
rescue Exception => e
  puts "Nice try, buddy."
end
puts "And on we run..."

#=> "Nice try, buddy."
#=> "And on we run..."

---

注意这个例子不会在（一些版本的？）IRB中运行，IRB提供了自己的退出方法来掩盖正常的对象＃退出。

---

Note that this example will not work in (some versions of?) IRB, which supplies its own exit method that masks the normal Object#exit.

在1.8.7中： / p>

In 1.8.7:

method :exit
#=> #<Method: Object(IRB::ExtendCommandBundle)#exit>

在1.9.3中：

method :exit
#=> #<Method: main.irb_exit>

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