Embarcadero Delphi Use of try, except, and finally Exception-safe return of a new object
Example
When a function returns an object (as opposed to using one that's passed in by the caller), be careful an exception doesn't cause the object to leak.
function MakeStrings: TStrings;
begin
// Create a new object before entering the try-block.
Result := TStringList.Create;
try
// Execute code that uses the new object and prepares it for the caller.
Result.Add('One');
MightThrow;
except
// If execution reaches this point, then an exception has occurred. We cannot
// know how to handle all possible exceptions, so we merely clean up the resources
// allocated by this function and then re-raise the exception so the caller can
// choose what to do with it.
Result.Free;
raise;
end;
// If execution reaches this point, then no exception has occurred, so the
// function will return Result normally.
end;
Naive programmers might attempt to catch all exception types and return nil from such a function, but that's just a special case of the general discouraged practice of catching all exception types without handling them.
