How should I re-raise a Delphi exception after logging it?

Question

Do you know a way to trap, log, and re-raise exception in Delphi code? A simple example:

procedure TForm3.Button1Click(Sender: TObject);
begin
  try
    rais         


        

Answer 1

The following will work, but is of course not ideal for 2 reasons:

• The exception is raised from a different place in the call stack.
• You don't get an exact copy of the exception - especially those classes that add attributes. I.e. you'll have to explicitly copy the attributes you need.
• Copying custom attributes can get messy due to required type checking.

.

procedure TForm3.MyHandleException(AException: Exception);
begin
  ShowMessage(AException.Message);
  LogThis(AException.Message);  
  raise ExceptClass(AException.ClassType).Create(AException.Message);
end;

The benefits are that you preserve the original exception class, and message (and any other attributes you wish to copy).

Ideally you'd want to call System._RaiseAgain, but alas that is a 'compiler-magic' routine and can only be called by raise;.