How to make my VBA code look better and reduce redundancy? - vba

Question

I have written very ugly VBA code, but I don't know how I can make this look better.
I have a function (say Function Main) that calls another 3 functions inside it. These 3 functions have to happen in order, and if one fails, the rest shouldn't happen. Also, I need to retrieve proper, descriptive error message. I have another software that invokes VBA code and calls this Main function, and if there is an error, I need to use that information, so I am returning a value (either a descriptive error message or "Completed") from Main as well.
Function Main
Dim result As String
result = ProcessA();
If result <> "OK" Then
Main = result
Exit Function
End If
result = ProcessB();
If result <> "OK" Then
Main = result
Exit Function
End If
result = ProcessC();
If result <> "OK" Then
Main = result
Exit Function
End If
Main = "Completed"
End Function
Function ProcessA()
On Error GoTo Errored
'Do some operation
ProcessA = "OK" 'At the end of operation, assign OK and
Exit Function 'Exit function here
Errored: 'In case of an error, get error information and return it
ProcessA = "Error Line: " & Erl & Chr(13) _
& "Error Description: " & Err.Description & Chr(13) _
& "Error at Process A"
End Function
'ProcessB and ProcessC also have a very similar style.
As you can see, my Main function has so many redundant code, but I can't think of any other better way. Could someone give me advice on how to make this better?

Answer 1

I would suggest re-throwing the error then catching it in the calling method:
Function Main()
On Error GoTo haveError
ProcessA
ProcessB
ProcessC
Main = "Completed"
Exit Function
haveError:
Main = err.Description
End Function
Sub ProcessA()
On Error GoTo Errored
'Do some operation
Exit Sub
Errored:
err.Raise Number:=err.Number, Description:=DescribeError(err, "ProcessA")
End Sub
Sub ProcessB()
On Error GoTo Errored
'Do some operation
Debug.Print 1 / 0 'eg. error here....
Exit Sub
Errored:
err.Raise Number:=err.Number, Description:=DescribeError(err, "ProcessB")
End Sub
Sub ProcessC()
On Error GoTo Errored
'Do some operation
Exit Sub
Errored:
err.Raise Number:=err.Number, Description:=DescribeError(err, "ProcessC")
End Sub
'utility
Function DescribeError(err As ErrObject, procName As String)
DescribeError = "Error in method: " & procName & vbLf & _
"Error Line: " & erl & vbLf & _
"Error Description: " & err.Description
End Function

Answer 2

Function Main
Dim result As String
result = ProcessA(): If result <> "OK" Then goto errResult
result = ProcessB(): If result <> "OK" Then goto errResult
result = ProcessC(): If result <> "OK" Then goto errResult
Main = "Completed"
Exit Function
errResult:
Main=result
End Function

Answer 3

Private errorMsg As String
Function Main()
If ProcessA Then
If ProcessB Then
If ProcessC Then
Main = "Completed"
End If
End If
End If
If Main = vbNullString Then Main = errorMsg
End Function
Private Function ProcessA() As Boolean
ProcessA = True
Exit Function
Err:
ReportError "Process A"
End Function
Private Sub ReportError(argSrc As String)
errorMsg = "Error Line: " & Erl & Chr(13) _
& "Error Description: " & Err.Description & Chr(13) _
& "Error at " & argSrc
End Sub

Answer 4

Using Application.Run(), you can process any number of steps in a loop:
Function Main()
Dim f, result
For Each f In Array("ProcessA", "ProcessB", "ProcessC") ' and so on
result = Application.Run(f)
If result <> "OK" Then
Main = result
Exit Function
End If
Next
Main = "Completed"
End Function