Use a non-public array from another module within a new module - arrays

Question

I am following a tutorial on VBA static arrays. I want to make sure my thought process is correct for something simple that I wish to do.
I have code that picks up all 12 months and places it into a static array of type string. As practice, I wanted to see if it's possible to copy these values onto another location using another module that acts as "pasting" the months at the cursor selection, but not utilizing a public array. I'm new to VBA so perhaps my way of think about coding is flawed and for such a purpose, I should be using a publicly defined array.
Sub PopulateStaticArray()
Dim months(11) As String
Dim ndx As Integer
Dim xrow As Long
ndx = 0
xrow = 2
Do Until Cells(xrow, 1).Value = ""
months(ndx) = Cells(xrow, 1).Value
ndx = ndx + 1
xrow = xrow + 1
Loop
End Sub
What I want to achieve in a redundant fashion. (I'm essentially recreating the array from scratch).
Sub InsertMonthsArray()
Dim counter As Integer
Dim rowNum As Double
Dim colNum As Double
Dim months(11) As String
ActiveCell.Select
rowNum = ActiveCell.Row
colNum = ActiveCell.Column
months(0) = "January"
months(1) = "February"
months(2) = "March"
months(3) = "April"
months(4) = "May"
months(5) = "June"
months(6) = "July"
months(7) = "August"
months(8) = "September"
months(9) = "October"
months(10) = "November"
months(11) = "December"
For counter = 0 To UBound(months, 1)
Cells(rowNum, colNum).Value = months(counter)
rowNum = rowNum + 1
Next counter
End Sub
I read some posts about passing arrays, but I'm not sure if that's achieving what I'm looking for. Of course this is not actual project, but just to improve my understanding of the interaction between modules within VBA for Excel. I don't necessary need any code, but just the general conceptual guidance on if I should be using some other method to achieve this task (i.e. Public defined Array or Functions, etc.) Thank you.

Answer 1

#GSerg mentioned correctly
"You are not creating a static array inside PopulateStaticArray. If you want to pass an already existing array to InsertMonthsArray(), regardless of where it comes from, then yes, that should be Sub InsertMonthsArray(months() as string)"
You need to pass your array - declared at procedure level - as (implicit) ByRef argument, which means that you can assign month names to each array item within the called sub procedure createMonths so that the calling procedure can actually use them, for instance to write them to a vertical range (e.g. starting at cell A7).
Option Explicit ' declaration head of code module
Sub PopulateMonthArray()
'[0] declare array at procedure level
Dim months(11) As String ' equals Dim months(0 to 11)
'Dim months(1 To 12) As String ' alternative: declare a 1-based array
'[1] fill array items with month names passing array as (implicit) ByRef argument
createMonths months ' << call sub createMonths
'[2] write 1-dim array vertically to sheet (transposing output from a "flat" to a 2-dim array)
Sheet1.Range("A7").Resize(Rowsize:=12).Value = Application.Transpose(months)
End Sub
Sub procedure createMonths
As you define a 0-based array months(0 To 11) and months count usually from 1 to 12 I added functionality to allow to create a 1-based array as well.
Sub createMonths(months) ' equals Sub createMonths(ByRef months)
Dim countOffset As Long
countOffset = IIf(LBound(months), 0, 1) ' allow calculation of 0-based AND 1-based arrays
Dim i As Long
For i = LBound(months) To UBound(months) ' loop through each array element
months(i) = Application.Text(DateSerial(0, i + countOffset, 1), "mmmm")
Next i
End Sub
Simple alternative /Edit 2020-05-27
If your intention is, however to make your months array disponible within other procedures without need to declare it in each procedure (neither at a global scope nor within a class definition), you could simply profit from a simple workaround: insert a Property Get usable in standard modules, too - not only available in class modules btw. - But note that you don't preserve ("retain") the array actually, you would rebuild it and possibly in a better readable way.
Public Property Get Months()
Dim tmp(1 To 12) ' I'd prefer a 1-based months array :-)
createMonths tmp ' use the same procedure as above (or rebuild it code)
Months = tmp ' return the Get value
End Property
Sub AnyOtherProcedure()
'no further declaration needed
Debug.Print Months(1) ' ~> January
Debug.Print Join(Months, ", ") ' ~> January, February, ..., December
End Sub