OpenOffice.org BASIC Guide.pdf - OpenOffice.org wiki

Error Handling 38
Sub Test
On Error Resume Next
' ... perform task during which an error may occur
End Sub
Use the On Error Resume Next command with caution as its effect is global.
Queries Regarding Error Information
In error handling, it is useful to have a description of the error and to know where and why
the error occurred:
• The Err variable contains the number of errors that has occurred.
• The Error$ variable contains a description of the error.
• The Erl variable contains the line number where the error occurred.
The call
MsgBox "Error " & Err & ": " & Error$ & " (line : "
& Erl & ")"
shows how the error information can be displayed in a message window.
Whereas VBA summarizes the error messages in a statistical object called Err, OpenOffice.org Basic
provides the Err, Error$, and Erl variables.
The status information remains valid until the program encounters a Resume or On Error
command, whereupon the information is reset.
In VBA, the Err.Clear method of the Err object resets the error status after an error occurs. In
OpenOffice.org Basic, this is accomplished with the On Error or Resume commands.
Tips for Structured Error Handling
Both the definition command, On Error, and the return command, Resume, are variants of
the Goto construct.
If you want to cleanly structure your code to prevent generating errors when you use this
construct, you should not use jump commands without monitoring them.
Care should be taken when you use the On Error Resume Next command as this dismisses
all open error messages.
The best solution is to use only one approach for error handling within a program - keep
error handling separate from the actual program code and do not jump back to the original
code after the error occurs.
The following code is an example of an error handling procedure:
Sub Example
' Define error handler at the start of the function