Example: Complex error handling within a subroutine

The following example code shows a complicated error handler for a subroutine. When an error occurs, the code jumps to the
ErrHandler:
 label. At this point the
Err.Number
 property is used to format the error message. The code determines whether the subroutine is running in
FactoryTalk View Studio
 or the
FactoryTalk View SE
 Client.
  • If it is running in test run mode in
    FactoryTalk View Studio
    , a message is displayed presenting the option to debug the code and the subroutine jumps back to the line that caused the error.
  • If it is running in the
    FactoryTalk View SE
     Client, an error is logged to FactoryTalk Diagnostics on the
    FactoryTalk View SE
     Client.
Sub ExampleComplexErrorHandling()  
  Dim oDisplay As DisplayClient.Display
  Dim sDispName As String
  ' Set the Error handler to jump to the ErrHandler: label on any error condition.
  On Error GoTo ErrHandler
  ' Set the display object to a display that is not loaded.
  ' In this example the string variable sDispName holds the display's name.
  sDispName = "Unknown Display"
  Set oDisplay = Application.LoadedDisplays(sDispName)
  ' Code may or may not reach the next line, depending on the actions taken in the error handler.
  oDisplay.SetFocus
Exit Sub
ErrHandler:
  Dim sErrMsg As String
  If Err.Number = gfxErrorConstants.gfxErrorCollectionIndex Then
    sErrMsg = "ExampleComplexErrorHandling():" & vbCrLf & "Display '" & sDispName & "' was not Found."
  Else
  sErrMsg = "ExampleComplexErrorHandling():" & vbCrLf & "Error Occurred: # " & Err.Number & ", " & Err.Description
  End If
  If Application.Name = "Graphics" Then
    ' Running in FactoryTalk View Studio
    If MsgBox(sErrMsg & vbCrLf & vbCrLf & "Do You Want to Debug?", vbYesNo Or vbQuestion) = vbYes Then
      ' if Yes was clicked, the following "Stop" statement stops the code
      Stop
      ' the F8 key is used from here to step through the code using
      ' the following "Resume" statement to return to the
      ' line that caused the error so the problem can be diagnosed and fixed.
      Resume
    End If
  Else
    ' Running in the SE Client (should not use MsgBox() call here)
    ' Here we use the replace command to change the formatting of the error message's CR-LF to a space.
    Application.LogDiagnosticMessage Replace(sErrMsg, vbCrLf, " "), ftDiagSeverityError 
    ' Resume running on the next statement.
    Resume Next
  End If
End Sub
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