> -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On > Behalf Of Wilfried Mestdagh > Sent: 13 January 2007 17:07 > To: twsocket@elists.org > Subject: Re: [twsocket] WinSock error 10035 with TWSocketServer > > Hello Bevan, > > I'm not a CBuilder specialis but: > > > AnsiString msg = ((TWSocketClient*) Sender)->ReceiveStr(); > > This is a good typecast. It tells the compiler that Sender is of type > TWSocketClient, so compiler can do the exact address offset > calculations within the type. You still have to check if msg is > "". >
Its ok if you are sure that Sender is a TWSocketClient. Otherwise its very unsafe. > > TWSocketClient* Client = dynamic_cast<TWSocketClient*>(Sender); > > AnsiString msg = Client->ReceiveStr(); > > The first line will execute, I think the second line will generate an > exception here. I'm not sure. Did you have it into an exception block ? > > As far as I know the dynamic_cast is a kind of equivalent for 'is' or > 'as' operators in Delphi and some other languages. It is not the same as > a type cast. I even think it will evaluate to false (null) because > Sender is of type TObject (yeah it "is" TWSocketClient, but compiler > dont know that). A dynamic cast is safer. Yes its similar to Delphi's as/is operators. In this case, this a pointer dynamic cast (rather than a reference), it will return null/nil if Sender isn't really a TWSocketClient, and the code should then check for this. An alternative is to use a reference: TWSocketClient& Client = dynamic_cast<TWSocketClient&>(Sender); which will throw an exception if Sender isn't a TWSocketClient at runtime. This is the safest way, it's better to have an exception than to treat an object as a different class (which could result in memory corruption). Dan -- To unsubscribe or change your settings for TWSocket mailing list please goto http://www.elists.org/mailman/listinfo/twsocket Visit our website at http://www.overbyte.be
