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4341 :: Iterator finalizer

• xzfc (orginal) [2018-10-30T05:15:09+01:00] view original

  Is there a way to have an iterator finalizer? It can be used to release allocated resources (close files, disconnect, etc) in case of break or if an exception is thrown.

  Consider the following example:

  iterator foo(): int =
    var a = init()
    while a.hasNext():
      yield a.nextValue()
    a.cleanup()
  
  for i in foo():
    discard # OK
  
  for i in foo():
    if i == 0:
      break # Bad: cleanup() is not called
  Run

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• Araq (orginal) [2018-10-30T10:52:19+01:00] view original

  Put the a.cleanup() in a try finally statement.

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• xzfc (orginal) [2018-10-30T15:08:29+01:00] view original

  Nice, thank you.

  Updated example for the completeness:

  iterator foo(): int =
    var a = init()
    try:
      while a.hasNext():
        yield a.nextValue()
    finally:
      a.cleanup()
  Run

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