ExternalException

Description

Occurs when an OLE automation command caused an exception on the OLE server.

NoteImproved error-handling capability in PowerBuilder The ExternalException event is maintained for backward compatibility. If you do not script this event or change its action argument, information from this event is passed to RuntimeError objects, such as OLERuntimeError. You can handle these errors in a try-catch block.

Event ID

Event ID

Objects

None

OLE, OLEObject, OLETxnObject

Arguments

Argument

Description

resultcode

UnsignedLong by value (a PowerBuilder number identifying the exception that occurred on the server).

exceptioncode

UnsignedLong by value (a number identifying the error that occurred on the server. For the meaning of the code, see the server documentation).

source

String by value (the name of the server, which the server provides).

description

String by value (a description of the exception, which the server provides).

helpfile

String by value (the name of a Help file containing information about the exception, which the server provides).

helpcontext

UnsignedLong by value (the context ID of a Help topic in helpfile containing information about the exception, which the server provides).

action

ExceptionAction by reference.

A value you specify to control the application’s course of action as a result of the error. Values are:

  • ExceptionFail! – fail as if this script were not implemented. The error condition triggers the SystemError event.

  • ExceptionIgnore! – ignore this error and return as if no error occurred (use this option with caution because the conditions that caused the error can cause another error).

  • ExceptionRetry! – execute the function or evaluate the expression again in case the OLE server was not ready.

  • ExceptionSubstituteReturnValue! – use the value specified in the returnvalue argument instead of the value returned by the OLE server or DataWindow and cancel the error condition.

returnvalue

Any by reference.

A value whose datatype matches the expected value that the OLE server would have returned. This value is used when the value of action is ExceptionSubstituteReturnValue!.

Returns

None. (Do not use a RETURN statement.)

Usage

OLE objects are dynamic. Expressions that refer to data and properties of these objects might be valid under some runtime conditions but not others. If the expression causes an exception on the server, PowerBuilder triggers the ExternalException event. The ExternalException event gives you information about the error that occurred on the OLE server.

The server defines what it considers exceptions. Some errors, such as mismatched datatypes, generally do not cause an exception but do trigger the Error event. In some cases you might not consider the cause of the exception to be an error. To determine the reason for the exception, see the documentation for the server.

When an exception occurs because of a call to an OLE server, error handling occurs like this:

  1. The ExternalException event occurs.

  2. If the ExternalException event has no script or its action argument is set to ExceptionFail!, the Error event occurs.

  3. If the Error event has no script or its action argument is set to ExceptionFail!, any active exception handler for an OLERuntimeError or its RuntimeError ancestor is invoked.

  4. If no exception handler exists, or if the existing exception handlers do not handle the exception, the SystemError event is triggered.

  5. If the SystemError event has no script, an application error occurs and the application is terminated.

Examples

Example 1

Suppose your window has two instance variables: one for specifying the exception action, and another of type Any for storing a potential substitute value. Before accessing the OLE property, a script sets the instance variables to appropriate values:

ie_action = ExceptionSubstituteReturnValue!

ia_substitute = 0

li_currentsetting = ole_1.Object.Value

Example 2

If the command fails, a script for the ExternalException event displays the Help topic named by the OLE server, if any. It substitutes the return value you prepared and returns control to the calling script. The assignment of the substitute value to li_currentsetting works correctly because their datatypes are compatible:

string ls_context


// Command line switch for WinHelp numeric context ID

ls_context = "-n " + String(helpcontext)

If Len(HelpFile) > 0 THEN

   Run("winhelp.exe " + ls_context + " " + helpfile)

END IF


action = ie_action 

returnvalue = ia_substitute 

Because the event script must serve for every automation command for the control, you need to set the instance variables to appropriate values before each automation command.

See also