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Event Driven Programming

ReDim Cells(1 To 100, 10) As Integer
...
ReDim Preserve Cells(1 To 100, 20) As Integer ‘ This works.
ReDim Preserve Cells(1 To 200, 20) As Integer ‘ This doesn’t.
Finally, you can destroy an array using the Erase statement. If the array is dynamic, Visual Basic
releases the memory allocated for its elements (and you can’t read or write them any longer);
if the array is static, its elements are set to 0 or to empty strings.
You can use the LBound and UBound functions to retrieve the lower and upper indices. If the
array has two or more dimensions, you need to pass a second argument to these functions to
specify the dimension you need:
Print LBound(Cells, 1) ‘ Displays 1, lower index of 1st dimension
Print LBound(Cells) ‘ Same as above
Print UBound(Cells, 2) ‘ Displays 20, upper index of 2nd dimension
’ Evaluate total number of elements.
NumEls = (UBound(Cells) _ LBound(Cells) + 1) * _
(UBound(Cells, 2) _ LBound(Cells, 2) + 1)

7.1.4 Arrays within UDTs

UDT structures can include both static and dynamic arrays. Here’s a sample structure that contains
both types:
Type MyUDT
StaticArr(100) As Long
DynamicArr() As Long
End Type

...
Dim udt As MyUDT
’ You must DIMension the dynamic array before using it.
ReDim udt.DynamicArr(100) As Long
’ You don’t have to do that with static arrays.
udt.StaticArr(1) = 1234
The memory needed by a static array is allocated within the UDT structure; for example, the
StaticArr array in the preceding code snippet takes exactly 400 bytes. Conversely, a dynamic
array in a UDT takes only 4 bytes, which form a pointer to the memory area where the actual
data is stored. Dynamic arrays are advantageous when each individual UDT variable might host
a different number of array items. As with all dynamic arrays, if you don’t dimension a dynamic
array within a UDT before accessing its items, you get an error 9—”Subscript out of range”.

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