多重继承往往导致virtual base classes(虚拟基类)的需求.在non-virtual base的情况下,如果派生类对于基类有多条继承路径,那么派生类会有不止一个基类部分,让基类为virtual可以消除这样的复制现象.然而虚基类也可能导致另一成本:其实现做法常常利用指针,指向"virtual base class"部分,因此对象内可能出现一个
虚拟继承下 Virtual Function 的语意 考虑下面的 virtual base class 派生体系: classPoint2d {public: Point2d(float=0.0,float=0.0);virtual~Point2d();virtualvoidMumble();virtualfloatZ();//...protected:float_x, _y; };classPoint3d:publicvirtualPoint2d {public: Point3d(float=0.0,float=0.0,float=...
virtual机制说的自然是virtual base class机制。 你的第一个例子里面说的：“除非visual机制才可以直接...
class Base { public: FunctionPointer *__vptr; virtual void function1() {}; virtual void function2() {}; }; class D1: public Base { public: virtual void function1() {}; }; class D2: public Base { public: virtual void function2() {}; }; 因为有2个虚函数因此虚函数表有2个指针...
pure virtual function 虚纯函数是基类中的函数模板,必须在派生类中用新代码重写。 总结一下:对于virtual function ,是在base中提供了一个函数模板,但不是必须进行override,但对于pure virtual function 而言,必须进行override,如果你忘记override,则会出现编译错误,也起了一种提示作用。
classDog:publicAnimal{ public: voideat(){ cout<<"dog eat"<<endl; Animal::die();//use base class's function } }; classCat:publicAnimal{ public: voideat(){ cout<<"cat eat"<<endl; } }; classLion:publicAnimal{ }; int_tmain(intargc,_TCHAR*argv[]) ...
The virtual keyword declares a virtual function or a virtual base class. virtual [type-specifiers] member-function-declarator virtual [access-specifier] base-class-name Parameters type-specifiers Specifies the return type of the virtual member function. ...
If a class introduces a virtual function member and the class has a non- virtual base class with a virtual function table pointer, then the class shares the virtual function table pointer of the non-virtual base class that is first visited in a depth-first, left-to- right traversal of ...
If a derived class overrides a virtual function that it inherits from a virtual base class, and if a constructor or a destructor for the derived base class calls that function using a pointer to the virtual base class, the compiler may introduce additional hidden "vtordisp" fields into the c...
A virtual function is a member function that you expect to be redefined in derived classes. When you refer to a derived class object using a pointer or a reference to the base class, you can call a virtual function for that object and execute the derived class's version of the function....