merge several bits of data from different sheets - arrays

Question

I am trying to merge several bits of data from different sheets. After a few questions and attempts (at arrays, thanks to Stackoverflow before for help with this), i think a dictionary may be best. The final outcome is a populated table that holds all data for each individual entry. (depending on the entry the data in a column in raw data could be in different locations)
The data can include multiple entries for one person. But the data for each entry is different depending on the stage of entry. For example, if the data in column 3 would be in column 5 of the final table if a condition was stage 1, however if condition was stage 2, the same data that was in column 3 could be column 10 of the final table.
https://www.youtube.com/watch?v=o8fSY_4p93s
Following this video tutorial ondictionaires, i think i could o through the dtaa and find each individual entry and then add the corresponding variables for the case. E.g. find data for Steve Smith, if steve smith exists then if stage 1, add data to variable stagedate1, if stage2 add data to stage2date and so on. If not found add entry and find the stage.
Similar to the video, where he finds the corresponding data for each customer, and adds sales and volumes, i could do the same if an if function is round before to identify which datastage and to then put the value in correct variable.
I know there will be a million way to do it, but this seems simple and effective.
Sub Dictionary()
Dim dict As Dictionary
Set dict = ReadData()
Call WriteDict(dict)
End Sub
Function ReadData()
Dim dict As New Dictionary
Dim DataWs As Worksheet: Set DataWs = ThisWorkbook.Sheets("DATA")
Dim PoolOfWeekWs As Worksheet: Set PoolOfWeekWs = ThisWorkbook.Sheets("Pool of the week")
Dim LastrowData As Long: LastrowData = DataWs.range("A" & Rows.Count).End(xlUp).Row
Dim LastColData As Long: LastColData = DataWs.Cells(1 & DataWs.Columns.Count).End(xlToLeft).Column
Dim LastColDataString As String: LastColDataString = Split(Cells(1, LastColData).Address, "$")(1)
Dim DataRange As range: Set DataRange = DataWs.range("A1:" & LastColDataString & LastrowData)
Dim DataArr As Variant: DataArr = DataWs.range("A1:AO" & LastrowData)
Dim range As range: Set range = DataWs.range("A1").CurrentRegion
Dim i As Long
Dim CandidateProcessID As String, CandidateName As String, FirstName As String, ProcessStatus As String, PQLDate As Date, oCandidate As ClsCandidate
For i = 2 To range.Rows.Count
CandidateProcessID = range.Cells(i, 10).Value
CandidateName = range.Cells(i, 16).Value
FirstName = range.Cells(i, 17).Value
ProcessStatus = range.Cells(i, 9).Value
If dict.Exists(CandidateProcessID) = True Then
Set oCandidate = dict(CandidateProcessID) 'CODE ERRORS HERE AFTER A FEW ROWS (Comes across a
Else an entry that is already in the dictionary)
Set oCandidate = New ClsCandidate
dict.Add CandidateProcessID, oCustomer
End If
oCandidate.CandidateName = oCandidate.CandidateName
oCandidate.FirstName = oCandidate.FirstName
oCandidate.ProcessStatus = oCandidate.ProcessStatus
oCandidate.PQLDate = oCandidate.PQLDate
Next i
Set ReadData = dict
End Function
Sub WriteDict(dict As Dictionary)
Dim key As Variant, oCandidate As ClsCandidate
For Each key In dict
Set oCandidate = dict(key)
Debug.Print key, oCandidate.CandidateName, oCandidate.FirstName, oCandidate.ProcessStatus, oCandidate.PQLDate
Next key
End Sub

Answer 1

I believe the error is object error. It stops and debugs.
That would be "Object Required", and it's absolutely consistent with a very common trap: add Option Explicit at the top of every module, and now VBA won't let you run the code until it knows what oCustomer is.
Option Explicit being missing has allowed the code to run with oCustomer undeclared: simply, a new Variant/Empty pointer is created on-the-spot for that local identifier ("oCustomer"), such that every iteration that "works" is just preparing the ground to make the ones that don't, blow up:
If dict.Exists(CandidateProcessID) = True Then
Set oCandidate = dict(CandidateProcessID) '<~ Variant/Empty is retrieved here: "object required"
Else
Set oCandidate = New ClsCandidate
dict.Add CandidateProcessID, oCustomer '<~ Variant/Empty is added here
End If
The Variant/Empty is successfully retrieved from the dictionary: the problem is that the Set oCandidate instruction on the left side of that = operator says the right-hand side of the operation must be an object reference. Variant/Empty fails to satisfy this requirement, and an "object required" run-time error is raised.
The bug isn't with the retrieval: it's with the storage!
You can easily find bugs like this with static code analysis tooling, such as Rubberduck (disclosure: that's my website).