C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  what's the trick of making virtual destructor protedted?          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message daniel Guest Posted: Mon Jul 03, 2006 8:29 am    Post subject: what's the trick of making virtual destructor protedted? I wonder if there is any reasonable reason to make virtual destructor protected within a derived class purposely? Back to top Jerry Coffin Guest Posted: Mon Jul 03, 2006 9:03 am    Post subject: Re: what's the trick of making virtual destructor protedted? In article <1151897380.688686.137500 (AT) a14g2000cwb (DOT) googlegroups.com>, daniel.huangfei (AT) gmail (DOT) com says... Quote: I wonder if there is any reasonable reason to make virtual destructor protected within a derived class purposely? A virtual protected dtor will normally be accompanied by a static member function to create objects. The dtor is protected to prevent outside code from creating instances of the class without using the static member function to create them. Making it virtual and protected means this is intended to be used as a base class. -- Later, Jerry. The universe is a figment of its own imagination. Back to top Shimin Guest Posted: Mon Jul 03, 2006 9:10 am    Post subject: Re: what's the trick of making virtual destructor protedted? Jerry Coffin wrote: Quote: In article <1151897380.688686.137500 (AT) a14g2000cwb (DOT) googlegroups.com>, daniel.huangfei (AT) gmail (DOT) com says... I wonder if there is any reasonable reason to make virtual destructor protected within a derived class purposely? A virtual protected dtor will normally be accompanied by a static member function to create objects. The dtor is protected to prevent outside code from creating instances of the class without using the static member function to create them. Making it virtual and protected means this is intended to be used as a base class. Are you confusing _dtor_ with _ctor_? Shimin Back to top Alf P. Steinbach Guest Posted: Mon Jul 03, 2006 9:10 am    Post subject: Re: what's the trick of making virtual destructor protedted? * Shimin: Quote: Jerry Coffin wrote: In article <1151897380.688686.137500 (AT) a14g2000cwb (DOT) googlegroups.com>, daniel.huangfei (AT) gmail (DOT) com says... I wonder if there is any reasonable reason to make virtual destructor protected within a derived class purposely? A virtual protected dtor will normally be accompanied by a static member function to create objects. The dtor is protected to prevent outside code from creating instances of the class without using the static member function to create them. Making it virtual and protected means this is intended to be used as a base class. Are you confusing _dtor_ with _ctor_? No, he's confusing two different schemes for ensuring dynamic allocation: (1) using factory factions, and (2) using protected or private destructor, where the main advantage is that you /don't/ have to create a factory function per constructor. See section 1.1.3 of <url: http://home.no.net/dubjai/win32cpptut/special/pointers/ch_01.pdf>. -- A: Because it messes up the order in which people normally read text. Q: Why is it such a bad thing? A: Top-posting. Q: What is the most annoying thing on usenet and in e-mail? Back to top daniel Guest Posted: Mon Jul 03, 2006 9:10 am    Post subject: Re: what's the trick of making virtual destructor protedted? Jerry Coffin wrote: Quote: In article <1151897380.688686.137500 (AT) a14g2000cwb (DOT) googlegroups.com>, daniel.huangfei (AT) gmail (DOT) com says... I wonder if there is any reasonable reason to make virtual destructor protected within a derived class purposely? A virtual protected dtor will normally be accompanied by a static member function to create objects. The dtor is protected to prevent outside code from creating instances of the class without using the static member function to create them. Making it virtual and protected means this is intended to be used as a base class. -- I think the destructor has nothing to do with the way that the object is created, so I guess you are talking about constructor? or did I miss anything? will the protected destructor effect the way that my object is destroyed? thanks again. daniel Quote: Later, Jerry. The universe is a figment of its own imagination. Back to top Alf P. Steinbach Guest Posted: Mon Jul 03, 2006 9:10 am    Post subject: Re: what's the trick of making virtual destructor protedted? * Alf P. Steinbach: Quote: * Shimin: Jerry Coffin wrote: In article <1151897380.688686.137500 (AT) a14g2000cwb (DOT) googlegroups.com>, daniel.huangfei (AT) gmail (DOT) com says... I wonder if there is any reasonable reason to make virtual destructor protected within a derived class purposely? A virtual protected dtor will normally be accompanied by a static member function to create objects. The dtor is protected to prevent outside code from creating instances of the class without using the static member function to create them. Making it virtual and protected means this is intended to be used as a base class. Are you confusing _dtor_ with _ctor_? No, he's confusing two different schemes for ensuring dynamic allocation: (1) using factory factions, and (2) using protected or private destructor, where the main advantage is that you /don't/ have to create a factory function per constructor. See section 1.1.3 of <url: http://home.no.net/dubjai/win32cpptut/special/pointers/ch_01.pdf>. 1.3.3, sorry. -- A: Because it messes up the order in which people normally read text. Q: Why is it such a bad thing? A: Top-posting. Q: What is the most annoying thing on usenet and in e-mail? Back to top daniel Guest Posted: Mon Jul 03, 2006 9:10 am    Post subject: Re: what's the trick of making virtual destructor protedted? thank you all for helping, I'll take a look at the related chapters in design pattern... cheers daniel. Back to top Jerry Coffin Guest Posted: Mon Jul 03, 2006 9:10 am    Post subject: Re: what's the trick of making virtual destructor protedted? In article <e8aah3$4qg$1 (AT) rumours (DOT) uwaterloo.ca>, smguo2001 (AT) gmail (DOT) com says... Quote: Jerry Coffin wrote: In article <1151897380.688686.137500 (AT) a14g2000cwb (DOT) googlegroups.com>, daniel.huangfei (AT) gmail (DOT) com says... I wonder if there is any reasonable reason to make virtual destructor protected within a derived class purposely? A virtual protected dtor will normally be accompanied by a static member function to create objects. The dtor is protected to prevent outside code from creating instances of the class without using the static member function to create them. Making it virtual and protected means this is intended to be used as a base class. Are you confusing _dtor_ with _ctor_? No -- the dtor has essentially the same effect. For example, if you create an object with automatic storage duration, it has to be destroyed when it goes out of scope. If the dtor is private or protected, you don't have access to the dtor, so the compiler won't allow you to create the automatic object. IOW, you can accomplish essentially the same thing with either the ctor or the dtor. -- Later, Jerry. The universe is a figment of its own imagination. Back to top daniel Guest Posted: Mon Jul 17, 2006 7:23 am    Post subject: Re: what's the trick of making virtual destructor protedted? thank you all for your great help! I've found the protected dtor will make an object be created from heap only, that is: using new operator. from this aspect, the trick is different from making ctor private or protected, in that way, object must be created through another member function. I think both are quite useful within certain contexts. thanks again.. daniel Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         C++Talk.NET Forum Index -> C++ language (comp.lang.c++) All times are GMT Page 1 of 1   Jump to: Select a forum C/C++----------------C LanguageC Language (Moderated)C++ Language (Moderated)C++ language (comp.lang.c++)C++ language, library and standards Non-English C/C++ Newsgroups----------------C++ (German)C++ (French)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.