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752 :: Catching exceptions

• zio_tom78 (orginal) [2015-01-14T11:01:25+01:00] view original

  In C++ there is an easy way to bind an exception variable to some name, e.g.:

  try {
      // ...
  }
  catch(const MyException &e) {
      // Use "e" to write a nice error message
  }
  Run

  In Nim however, the only way I figured to do the same looks a bit inelegant:

  try:
      # ...
  except MyException:
      let e = (ref MyException)(getCurrentException())
      # Use "e" to write a nice error message
  Run

  The Nim manual says nothing about this (it does not even mention the existence of getCurrentException …), nor was I able to find some example in the Nim/standard library source codes. What is the best, most Nim-ish way to do this?

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• Araq (orginal) [2015-01-14T11:47:33+01:00] view original

  For the use case you outline you can simply use getCurrentExceptionMsg.

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• zio_tom78 (orginal) [2015-01-14T11:51:21+01:00] view original

  My real case involves an exception type, ParserError, which contains the error message as well as other information (name of the file, line and column number, state of the parser…), so getCurrentExceptionMsg is not enough.

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• Araq (orginal) [2015-01-14T12:09:37+01:00] view original

  Well there is no better way then. It comes up rarely enough that we could never be bothered to implement except IOError, OSError as e (and e then needs to be of the common supertype of IOError and OSError).

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• zio_tom78 (orginal) [2015-01-14T12:17:27+01:00] view original

  Might be worthwile to update the documentation, in order to provide the example I posted above and mention getCurrentException and getCurrentExceptionMsg? I can make a PR, if you want.

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• Araq (orginal) [2015-01-14T12:28:34+01:00] view original

  Of course, go ahead please!

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• gradha (orginal) [2015-01-14T12:59:30+01:00] view original

  I did use to have an elet and evar templates, you may want to borrow ideas from there. Stopped using them because depending on compilation switches you can use evar incorrectly and logging of exception types is low priority.

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• LeuGim (orginal) [2015-01-14T17:41:38+01:00] view original

  Would be useful to have exceptions catching at compile-time too, or at least to have no-exceptions versions of staticRead and staticExec (that just return empty string in case of failure).

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