Virtual functions in C + +

Code:

1#include <iostream>2#include <cstring>3 4 using namespacestd;5 6 classbase{7      Public:8         Virtual voidfunc1 ();9         Virtual voidFunc2 ();Ten         voidfunc3 (); One         voidFunc4 (); A }; -  - voidbase::func1 () { thecout<<"Base func1"<<Endl; - } -  - voidBase::func2 () { +cout<<"Base Func2"<<Endl; - } +  A voidbase::func3 () { atcout<<"Base func3"<<Endl; - } -  - voidBase::func4 () { -cout<<"Base Func4"<<Endl; - } in  - classDerived1: Publicbase{ to      Public: +         voidFunc1 ();//virtual can omit -         //Char Func2 () {}; Error, virtual function return type needs to be consistent the         voidfunc3 (); *         CharFunc4 (); $ };Panax Notoginseng  - voidderived1::func1 () { thecout<<"Derived1 func1"<<Endl; + } A  the voidderived1::func3 () { +cout<<"Derived1 func3"<<Endl; - } $  $ CharDerived1::func4 () { -cout<<"Derived1 Func4 can change the return type"<<Endl; - } the  - classDERIVED2: Publicbase{Wuyi      Public: the         voidfunc1 (); - }; Wu  - voidderived2::func1 () { Aboutcout<<"Derived2 func1"<<Endl; $ } -  - intMain () { -  ABase *B; + Derived1 De1; theB = &De1; -B->func1 (); $B->func3 (); theB->Func4 (); the De1.func4 (); the  theDERIVED2 *PDe2; -PDe2 = (derived2*) &De1; inPde2->func1 (); the  the     return 0; About  the}

Output:

Derived1 func1base func3base func4derived1 Func4 can change the return typeDerived1 func1

Summarize:

1, virtual function must be implemented in the parent class, do not implement can use pure virtual function;

2. The return type of a subclass virtual function must be the same as the return type in the parent class, and the normal function can be different;

3, subclass virtual function if the parameter changes, the virtual attribute disappears.

Virtual functions in C + +