Add Strings to Dynamic Array VBA - arrays

Question

Problem: I am comparing two columns of names. If a name from the primary column matches a name in the secondary column, then I would like to add the matching name to an array of strings.
Function 1: This boolean function should indicate whether there is a match:
Function Match(name As String, s As Worksheet, column As Integer) As Boolean
Dim i As Integer
i = 2
While s.Cells(i, column) <> ""
If s.Cells(i, column).Value = name Then
Match = True
End If
i = i + 1
Wend
Match = False
End Function
Function 2: This function should add the matching name to a dynamic array of strings. Here I am somewhat stuck as I am new to arrays- any suggestions?
Function AddToArray(ys) As String()
Dim a() As String
Dim size As Integer
Dim i As Integer
Dim sh As Worksheet
Dim rw As Range
size = 0
ReDim Preserve a(size)
For Each rw In sh.Rows
If Match(sh.Cells(rw.Row, 1), s, column) = True Then
??
size = size + 1
End Function

Answer 1

Here is one solution. I scrapped your Match function and replaced it with a Find function.
Option Explicit
Sub AddToArray()
Dim primaryColumn As Range, secondaryColumn As Range, matchedRange As Range
Dim i As Long, currentIndex As Long
Dim matchingNames As Variant
With ThisWorkbook.Worksheets("Sheet1")
Set primaryColumn = .Range("A1:A10")
Set secondaryColumn = .Range("B1:B10")
End With
'Size your array so no dynamic resizing is necessary
ReDim matchingNames(1 To primaryColumn.Rows.Count)
currentIndex = 1
'loop through your primary column
'add any values that match to the matchingNames array
For i = 1 To primaryColumn.Rows.Count
On Error Resume Next
Set matchedRange = secondaryColumn.Find(primaryColumn.Cells(i, 1).Value)
On Error GoTo 0
If Not matchedRange Is Nothing Then
matchingNames(currentIndex) = matchedRange.Value
currentIndex = currentIndex + 1
End If
Next i
'remove unused part of array
ReDim Preserve matchingNames(1 To currentIndex - 1)
'matchingNames array now contains just the values you want... use it how you need!
Debug.Print matchingNames(1)
Debug.Print matchingNames(2)
'...etc
End Sub
Extra comments
There is no need to create your own Match function because it already exists in VBA:
Application.Match()
WorksheetFunction.Match()
and as I mentioned above you can also achieve the same result with the Find function which is my preference here because I prefer the way you can check for no matches (other methods throw less convenient errors).
Finally, I also opted to restructure your code into one Sub rather than two Functions. You weren't returning anything with your AddToArray function which pretty much means by definition it should actually be a Sub

Answer 2

As I stated in a comment to the question, there are a couple of problems in your code before adding anything to the array that will prevent this from working, but assuming that this was caused by simplifying the code to ask the question, the following should work.
The specific question that you are asking, is how to populate the array while increasing its size when needed.
To do this, simply do this:
Instead of:
ReDim Preserve a(size)
For Each rw In sh.Rows
If Match(sh.Cells(rw.Row, 1), s, column) = True Then
Reorder this so that it is:
For Each rw In sh.Rows
If Match(sh.Cells(rw.Row, 1), s, column) = True Then
ReDim Preserve a(size) 'increase size of array
a(size) = sh.Cells(rw.Row,1) 'put value in array
size = size + 1 'create value for size of next array
End If
Next rw
....
This probably isn't the best way to accomplish this task, but this is what you were asking to do. First, increasing the array size EVERY time is going to waste a lot of time. It would be better to increase the array size every 10 or 100 matches instead of every time. I will leave this exercise to you. Then you could resize it at the end to the exact size you want.