如何确定数组是否在 VB6 中初始化? [英] How do I determine if an array is initialized in VB6?

问题描述

将未标注的数组传递给 VB6 的 Ubound 函数会导致错误，因此我想在尝试检查其上限之前先检查它是否已标注尺寸.我该怎么做?

Passing an undimensioned array to the VB6's Ubound function will cause an error, so I want to check if it has been dimensioned yet before attempting to check its upper bound. How do I do this?

推荐答案

这是我的想法.这类似于 GSerg 的 answer，但使用更好记录的 CopyMemory API 函数并且是完全独立的(您可以将数组而不是 ArrPtr(array) 传递给此函数).它确实使用了 VarPtr 函数，Microsoft 警告，但这是一个仅限 XP 的应用程序，而且它有效，所以我不担心.

Here's what I went with. This is similar to GSerg's answer, but uses the better documented CopyMemory API function and is entirely self-contained (you can just pass the array rather than ArrPtr(array) to this function). It does use the VarPtr function, which Microsoft warns against, but this is an XP-only app, and it works, so I'm not concerned.

是的，我知道这个函数会接受你扔给它的任何东西，但我会把错误检查留给读者作为练习.

Yes, I know this function will accept anything you throw at it, but I'll leave the error checking as an exercise for the reader.

Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" _
  (pDst As Any, pSrc As Any, ByVal ByteLen As Long)

Public Function ArrayIsInitialized(arr) As Boolean

  Dim memVal As Long

  CopyMemory memVal, ByVal VarPtr(arr) + 8, ByVal 4 'get pointer to array
  CopyMemory memVal, ByVal memVal, ByVal 4  'see if it points to an address...  
  ArrayIsInitialized = (memVal <> 0)        '...if it does, array is intialized

End Function

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