MS Access VBA loop stops without error or apparent cause - arrays

Question

I'm trying to compare two arrays of data in MS Access - one is generated from an API GET, and the other is generated from two columns of a table. I'm using a double loop to do the comparison, I suspect this isn't the best way but I'm still learning my way around loops and arrays. The code I'm using is as follows:
Sub ParseList(ResCount As Long)
Dim db As DAO.Database
Dim rstConts As DAO.Recordset
Dim midstr As String, emailstr As String, Fname As String, Lname As String, SubStatus As String, echeck As String, Mecheck As String, ArrEcheck As String, ArrMecheck As String, MSub As String
Dim ArrResp() As String
Dim ArrConts() As Variant
Dim SubStart As Long, SubCount As Long, Fstart As Long, Fcount As Long, Lstart As Long, LCount As Long, Diffcount As Long, c As Long, i As Long, t As Long, y As Long, u As Long, v As Long
Dim IsSub As Boolean
Set db = CurrentDb
Udate = SQLDate(Now)
ReDim ArrResp(1 To ResCount, 1 To 4) As String
'This section parses a JSON response into an array
For i = 1 To ResCount
midstr = ""
emailstr = ""
x = InStr(t + 2, GetListStr, "}}") + 21
y = InStr(x + 1, GetListStr, "}}")
If y = 0 Then
Exit Sub
End If
midstr = Mid(GetListStr, x, y - x)
emailstr = Left(midstr, InStr(midstr, ",") - 2)
SubStart = InStr(midstr, "Status") + 9
SubCount = InStr(InStr(midstr, "Status") + 8, midstr, ",") - SubStart - 1
SubStatus = Replace(Mid(midstr, SubStart, SubCount), "'", "''")
Fstart = InStr(midstr, ":{") + 11
Fcount = InStr(InStr(midstr, ":{") + 11, midstr, ",") - (Fstart + 1)
Fname = Replace(Mid(midstr, Fstart, Fcount), "'", "''")
Lstart = InStr(midstr, "LNAME") + 8
LCount = InStr(InStr(midstr, "LNAME") + 8, midstr, ",") - (Lstart + 1)
Lname = Replace(Mid(midstr, Lstart, LCount), "'", "''")
If SubStatus = "subscribed" Then
MSub = "True"
Else
MSub = "False"
End If
ArrResp(i, 1) = emailstr
ArrResp(i, 2) = MSub
ArrResp(i, 3) = Fname
ArrResp(i, 4) = Lname
t = y
Next i
'This section grabs two columns from a database table and adds them to a second array
Set rstConts = CurrentDb.OpenRecordset("SELECT Primary_Email, EMailings FROM TBLContacts")
rstConts.MoveLast
rstConts.MoveFirst
c = rstConts.RecordCount
ReDim ArrConts(1 To c) As Variant
ArrConts = rstConts.GetRows(c)
'This loops through the JSON response array, and when it finds a matching value in the Table array it checks if a second value in the table array matches or not
For u = 1 To ResCount
Debug.Print u
echeck = ArrResp(u, 1)
Mecheck = ArrResp(u, 2)
For v = 0 To c
If ArrConts(0, v) = "" Then
Else
ArrEcheck = ArrConts(0, v)
ArrMecheck = ArrConts(1, v)
If ArrEcheck = echeck Then
If ArrMecheck = Mecheck Then
Debug.Print echeck & "Match"
Else
Debug.Print echeck & "No Match"
End If
End If
End If
Next v
Next u
MsgBox "Done"
End Sub
The code above simply doesn't complete and the msgbox is never shown. The debug.print line near the end only goes to 1, and I can't figure out why. If I remove the conditions from the second loop section:
If ArrConts(0, v) = "" Then
Else
ArrEcheck = ArrConts(0, v)
ArrMecheck = ArrConts(1, v)
If ArrEcheck = echeck Then
If ArrMecheck = Mecheck Then
Debug.Print echeck & "Match"
Else
Debug.Print echeck & "No Match"
End If
End If
End If
Then I can successfully complete the Main loop, and receive the 'Done' message. But I've been unable to narrow down why the second loop isn't completing properly, and I'm stuck.

Answer 1

Because arrays are zero-indexed, you need to subtract 1 from the upper limit of nested For loop which should have thrown an error on the subsequent If line when loop exceeded the record limit.
For u = 1 To ResCount
Debug.Print u
echeck = ArrResp(u, 1)
Mecheck = ArrResp(u, 2)
For v = 0 To c - 1 ' REDUCE UPPER LIMIT BY 1
If ArrConts(0, v) = "" Then ' LINE NO LONGER SHOULD ERR OUT
...
Next v
Next u
With that said, consider parsing JSON to an MS Access table using the VBA-JSON library. Then use SQL to check values with JOIN and WHERE in set-based processing between table to table. This is much more efficient that looping between arrays.