Dynamic Array of dynamic arrays - arrays

Question

I can't seem to find this problem addressed anywhere.
I need to declare a bunch of dynamic arrays as follow:
Dim list1 () as variant
Dim list2() as variant
Dim list3() as variant
...
Dim listN() as Variant
Each list is a one-dimensional dynamic array. However, I wouldn't know what "N" will be during the program. I want to make these "N" lists dynamic as well. I have tried two-dimensional dynamic arrays. But the "redim" statement requires both dimensions to be declared at the same time. In particular, I do this:
Dim BigList() as variant
...
Redim BigList(listNum, listLength)
To access/pass into a sub "list1", "list2" , "list3"..., calling "BigList(1)", "BigList(2)" gives me error. In particular, somewhere in my code, there is this portion:
sub ProcessList(byref listToProcess() as variant)
...
end sub
sub main()
...
call ProcessList(list1)
call ProcessList(list2)
...
call ProcessList(listN)
end sub
Now I can do a loop:
for i = 1 to N
Call ProcessList(list"i")
next i
This requires list"i" to be a one-dimensional dynamic array. So, after a redim BigList(listNum,listLength) and I do this:
for i = 1 to N
Call ProcessList(BigList(i)) 'i refers to listNum
next i
This gives me error "Incompatible type".

Answer 1

Here is one example of creating a Dictionary which is keyed to integer values (i.e., the N) and each value is initially an empty array.
You can then use something like the ExtendList function to resize those empty arrays as needed.
Sub foo()
Dim BigList As Object
Dim N As Long
Dim v as Variant
'Create an empty dictionary object
Set BigList = CreateObject("Scripting.Dictionary")
'Add N empty array to the dictionary:
N = 3
For i = 1 To N
BigList(i) = Array()
Next
'Resize one of the items in your BigList
BigList(2) = ExtendList(BigList(2), 1, 10)
v = BigList(2) 'Here you can examine v in the Locals window and see it is an array, of dimensions 1 x 10
End Sub
Function ExtendList(lst, a As Long, b As Long)
ReDim lst(a, b)
ExtendList = lst
End Function
On review of your edited question, I think you merely misunderstood how the ReDim statement works:
Redim BigList(listNum, listLength)
This re-dimensions the BigList based on the parameters listNum and listLength. It does not (as it seems you may have expected) create a list of arrays within BigList.
I think this might also work (untested, and remember arrays are zero-index):
ReDim Preserve BigList(listNum)
BigList(listNum) = Array()
ReDim BigList(listNum)(listSize)