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Why Constructors Cannot Be Virtual

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What do I do? anywhere... Since virtual tables (and polymorphism in general) are all about polymorphic behaviour rather on polymorphic data , There is no sense with declaring a virtual constructor. So now it is clear that you can invoke the virtual funtion of derived class onlywith an object that has created.Now coming to virtual constructor,If we make constructor as virtual in http://macinstruct.net/cannot-be/why-constructors-cannot-be-considered-as-member-function.html

To critique or request clarification from an author, leave a comment below their post - you can always comment on your own posts, and once you have sufficient reputation you will I know this concept under the term "virtual copy constructor". Assume you are trying to create object of the class which has virtual constructor. How could a virtual constructor be useful or called?

Can Destructor Be Virtual

Please use code.geeksforgeeks.org, generate link and share the link here. joy asthana One should anyway remove these lines in order to avoid recompilation of consumers of Users-class - while( (input != Dealing With Dragonslayers How to handle swear words in quote / transcription? share|improve this answer answered Nov 23 '09 at 17:26 Marius 2,55411926 1 Wrong. But when we try to delete a delete a; it causes to call only the base destructor.So we have to handle the destructor using virtual keyword.

So virtual constructor is not possible but virtual destructor is.Thanks share|improve this answer answered Jun 23 '13 at 11:47 Tunvir Rahman Tusher 2,60811916 For virtual destructor try this link.stackoverflow.com/questions/461203/… A great way to see this is to look at the "Factory" pattern, especially factory functions. Then what about the dynamically allocated memory for an object? –nitin_cherian Dec 14 '11 at 15:28 2 @LinuxPenseur: When dynamically creating an object, the compiler still needs to know the Virtual Constructor In Java When there is new class addition (extension), the user needs to be aware of that class.

share|improve this answer answered Apr 14 '10 at 18:33 Rich 1,1171925 add a comment| up vote 1 down vote Cant we simply say it like.. Why Constructor Cannot Be Virtual But Destructor Can Consequently, a "call to a constructor" cannot be virtual. Enough theory, see the following code, #include using namespace std; //// LIBRARY START class Base { public: // The "Virtual Constructor" static Base *Create(int id); Base() { } virtual // Before construction, there is no object to do this.

Bug? Why Constructor Cannot Be Inherited In C++ In practical scenarios we would need to create a derived class object in a class hierarchy based on some input. What is the point of update independent rendering in a game loop? Was this answer useful?Yes 2 Reply Salim Aug 23rd, 2007 A virtual-table(vtable) is made for each Class having one or more 'virtual-functions'.

Why Constructor Cannot Be Virtual But Destructor Can

Virtual methods are used in polymorphism... When you construct an object the static type is always the same as the actual object type since: To construct an object, a constructor needs the exact type of the object Can Destructor Be Virtual Consequently, a "call to a constructor" cannot be virtual. Why Can't We Have Virtual Constructors How to prove that authentication system works, and that the customer is using the wrong password?

Is this description correct ? Before going into details, let us answer, who will dictate to create either of Derived1 or Derived2 object? vtables are static and constant. Now it tries to look for virtual constructor in derived. Why Constructor Cannot Be Static In C++

The core intention is to decouple tight binding between object creation and class type. As said, the intention is not to clutter the code with so many defensive techniques. 2. Please include your IP address in your email. http://macinstruct.net/cannot-be/why-virtual-functions-cannot-be-static.html Single word for the act of being susceptible?

Was this answer useful?Yes Reply EigenCritic Apr 6th, 2016 I will try to explain why there is no good reason we should have virtual constructors Virtual functions are used for Virtual Table In C++ so the virtual destructors is possible to make but not the virtual constructors. Secondly, what would happen in the case of multiple inheritance?

For one thing, the derived class will not be fully constructed at the time the virtual constructor is called, so there are potential issues with the implementation.

Constructor can not be virtual, because when constructor of a class is executed there is no vtable in the memory, means no virtual pointer defined yet. But the need is different. –nitin_cherian Dec 15 '11 at 6:30 I have modified the heading of the question. so there is no point of making the constructor as virtual. Virtual Functions In C++ Thing t; or new Whatever).

This is the reason why a constructor cannot be virtual answered Sep 29, 2015 by gauravsharma Please log in or register to add a comment. share|improve this answer answered Apr 9 '09 at 9:08 Pete Kirkham 38.3k267134 1 This is exactly the difference between construction in C++ and in a language such as Delphi, where BUT BUT Constructor of a class is never and ever extended by a derived, hence we will never heed to have a Virtual constructor.....That is U will never need to call Check This Out Now the point is, how you invoke the virtual function which is defined in derived class with the help of object of the class?Once you create an object of class, vptr

So virtual constructor is not possible but virtual destructor is.Thanks share|improve this answer answered Jun 23 '13 at 11:47 Tunvir Rahman Tusher 2,60811916 For virtual destructor try this link.stackoverflow.com/questions/461203/… share|improve this answer answered Jul 23 '15 at 21:55 user3726672 611 Constructors are not static, period. –curiousguy Aug 1 '15 at 5:48 This is obvious nonsense. share|improve this answer answered Dec 14 '11 at 15:22 Luchian Grigore 169k28301461 add a comment| up vote 1 down vote How would a constructor be able to be virtual? See users.rcn.com/jcoplien/Patterns/C++Idioms/… for some more information on how it's implemented –Tony Lee Sep 18 '09 at 18:16 add a comment| up vote 31 down vote two reasons I can think of:

How can the User class creates Derived3 object?