Ruby中的异常处理代码编写示例

    应该总是避免拦截(最顶级的) Exception 异常类。这里(ruby自身)将会捕获信号并且调用 exit，需要你使用 kill -9 杀掉进程。

 

  # bad
  begin
   # calls to exit and kill signals will be caught (except kill -9)
   exit
  rescue Exception
   puts "you didn't really want to exit, right?"
   # exception handling
  end

  # good
  begin
   # a blind rescue rescues from StandardError, not Exception as many
   # programmers assume.
  rescue => e
   # exception handling
  end

  # also good
  begin
   # an exception occurs here

  rescue StandardError => e
   # exception handling
  end

    将更具体的异常放在救援（rescue）链的上方，否则他们将不会被救援。

  # bad
  begin
   # some code
  rescue Exception => e
   # some handling
  rescue StandardError => e
   # some handling
  end

  # good
  begin
   # some code
  rescue StandardError => e
   # some handling
  rescue Exception => e
   # some handling
  end

    在 ensure 区块中释放你程式获得的外部资源。

  

 f = File.open('testfile')
  begin
   # .. process
  rescue
   # .. handle error
  ensure
   f.close unless f.nil?
  end

    除非必要, 尽可能使用 Ruby 标准库中异常类，而不是引入一个新的异常类。(而不是派生自己的异常类)