How do I determine if an array is initialized in VB6?

ghz 7months ago ⋅ 78 views

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?

Answers

To check if an array has been dimensioned in VB6 before attempting to use the UBound function, you can use the IsArray function in combination with error handling. VB6 does not provide a direct way to check if an array is dimensioned, but you can use a workaround by handling the error that UBound raises when it is passed an undimensioned array.

Here’s a function that encapsulates this logic:

Function IsArrayDimensioned(arr As Variant) As Boolean
    On Error Resume Next
    IsArrayDimensioned = IsArray(arr) And (Not IsError(LBound(arr)))
    On Error GoTo 0
End Function

Explanation

  1. IsArray(arr): Checks if arr is an array.
  2. LBound(arr): If arr is an undimensioned array, calling LBound will raise an error.
  3. Error Handling: The On Error Resume Next statement allows the code to continue executing even if an error occurs. If LBound causes an error, IsError(LBound(arr)) will return True.

Usage Example

Here’s how you can use the IsArrayDimensioned function:

Private Sub TestArrayDimensioning()
    Dim undimensionedArray() As String
    Dim dimensionedArray(1 To 10) As String

    If IsArrayDimensioned(undimensionedArray) Then
        MsgBox "The undimensionedArray is dimensioned."
    Else
        MsgBox "The undimensionedArray is not dimensioned."
    End If

    If IsArrayDimensioned(dimensionedArray) Then
        MsgBox "The dimensionedArray is dimensioned."
    Else
        MsgBox "The dimensionedArray is not dimensioned."
    End If
End Sub

Detailed Steps

  1. Declare the Arrays:

    • undimensionedArray is declared but not dimensioned.
    • dimensionedArray is declared and dimensioned from 1 to 10.

  2. Check if Arrays are Dimensioned:

    • Use IsArrayDimensioned to check the dimension status of each array.
    • Display a message box indicating whether each array is dimensioned or not.

By using this function, you can safely determine if an array has been dimensioned before calling UBound or performing other operations that require the array to be dimensioned. This helps in preventing runtime errors and ensures more robust code.

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