Virtual function in C++ Pure Virtual Function
Download as PPTX, PDF8 likes4,067 views
The document discusses runtime polymorphism and virtual functions in C++, illustrating their usage through examples. It explains the characteristics of abstract classes and pure virtual functions, emphasizing the concept that a class becomes abstract if it contains at least one pure virtual function, which lacks an implementation. Additionally, it highlights the impossibility of making static functions virtual and the application of default arguments in virtual functions.
Virtual function in C++ Pure Virtual Function
- 1. CE142 Runtime Polymorphism & Virtual Function
- 2. Virtual Function #include<iostream> using namespace std; class Base { public: virtual void show() { cout<<" In Base n"; } }; class Derived: public Base { public: void show() { cout<<"In Derived n"; } }; int main(void) { Base *bp = new Derived; bp->show(); // RUN-TIME POLYMORPHISM return 0; } In Derived
- 3. class A{ void f1(); virtual void f2(); virtual void f3(); virtual void f4(); }; class B:public A { void f2(); void f4(int x); void f1(); } Virtual Function &f2() &f3() &f4() _vtable &f2() &f3() &f4() _vtable A *p; A x1; p=&x1; p->f1(); p->f2(); p->f3(); p->f4(); p->f4(10); !!Error //EB //EB //LB //LB //LB p x1 _vptr
- 4. class A{ void f1(); virtual void f2(); virtual void f3(); virtual void f4(); }; class B:public A { void f2(); void f4(int x); void f1(); } Virtual Function &f2() &f3() &f4() _vtable &f2() &f3() &f4() _vtable A *p; B x1; p=&x1; p->f1(); p->f2(); p->f3(); p->f4(); p->f4(10); //EB //EB //LB //LB //LB p x1 _vptr
- 5. Can static functions be virtual in C++? #include<iostream> using namespace std; class Test { public: // Error: Virtual member functions cannot be static virtual static void fun() { } };
- 6. Virtual Function & Default Arguments #include <iostream> using namespace std; class Base { public: virtual void fun ( int x = 0 ) { cout << "Base::fun(), x = " << x << endl; } }; class Derived : public Base { public: void fun ( int x ) { cout << "Derived::fun(), x = " << x << endl; } }; int main() { Derived d1; Base *b = &d1; b->fun(); return 0; } "Derived::fun(), x =0
- 7. Virtual Function & Default Arguments #include <iostream> using namespace std; class Base { public: virtual void fun ( int x = 0 ) { cout << "Base::fun(), x = " << x << endl; } }; class Derived : public Base { public: void fun ( int x=10 ) //Note The Changes { cout << "Derived::fun(), x = " << x << endl; } }; int main() { Derived d1; Base *bp = &d1; bp->fun(); return 0; } "Derived::fun(), x =0
- 8. Can virtual functions be private in C++? Never. Why?
- 9. Abstract Classes in C++ No Implementation of function in base class is referred as Abstract class Example: class Shape having member function draw(). It can only be have implementation at derived classes. i.e. draw() in rectangle, draw() in square. Example: class Animal having member function move().
- 10. A class which does not have an implementations of the function. How to create abstract class in java. By putting abstract keyword before class definition How to create abstract class in C# By putting abstract keyword before class definition How to create abstract class in C++ By putting abstract keyword before class definition There is no abstract keyword in C++!!!!! Abstract class
- 11. How to create abstract class in C++ A class in C++ is abstract if it has at least one pure virtual function. What is pure virtual function? It is a kind of virtual function which has no implementations!!! Abstract class in C++
- 12. Error: Undefined reference to vtable for Sha How to make any function as pure virtual function
- 13. Abstract class in C++ How to create abstract class in C++ A class in C++ is abstract if it has at least one pure virtual function. What is pure virtual function? It is a kind of virtual function which has no implementations!!! How to make any virtual function as pure virtual function? By putting “=0” expression at function declaration.
- 14.
- 15. Characteristics of Abstract class in C++
- 16. 1. Abstract class may also contain non virtual functions.
- 17. 2. Instances of the abstract class can not be created.
- 18. 3. We can have pointers and references of abstract class type.
- 19. 4. If we do not override the pure virtual function in derived class, then derived class also becomes abstract class.
- 20. 5. An abstract class can have constructors.
- 22. Example
- 23. Example