Thanks to everybody. Sorry for delay. I received lots of emails today, for the whole week. I think Google Mail screw it up a little bit.
So, 'as' is safer than direct typecast. I think I will prefer this one. Thanks again. Doug Chamberlin wrote: > At 08:45 AM 2/26/2007, CubicDesign wrote: > >> (TObjectList[i] as TSomething) >> and >> TSomething(TObjectList[i]) >> >> Both codes access the same object; one is using the 'as' operator the >> second one is using a direct typecast. But what are the differences? >> > > The first one checks to see if TObjectList[1] is a TSomething (either > directly or through inheritance) and then treats the resulting reference as > a TSomething. If TObjectList[1] is NOT a TSomething a specific exception is > thrown that you can handle. > > TSomething(TObjectList[1]) forces the reference to be treated as a > TSomething without checking first. In this case any number of exceptions > can result if TObjectList[1] is not actually a TSomething. > > Some would argue that the second form is faster because it omits the check. > Others would argue that the second form is much more dangerous because of > the hidden assumption. The second form is much closer to the historic C > coding style which resulted in so many hard to find bugs or many years. > Most developers have moved past that style in favor of the more > conservative usage in the first example. > > > _______________________________________________ > Delphi mailing list -> [email protected] > http://www.elists.org/mailman/listinfo/delphi > > _______________________________________________ Delphi mailing list -> [email protected] http://www.elists.org/mailman/listinfo/delphi
