Polymorphism in C + +

I. Polymorphism definitions in C + +: Polymorphism is a technique that allows you to set a parent object to be equal to one or more of his child objects, and after assignment, the parent can operate differently depending on the attributes of the character object currently assigned to it. Simply put, in a nutshell: A pointer to the parent class type is allowed to assign a pointer to the child class type.

Two. Dynamic binding is the basis of polymorphism.

Definition of dynamic binding: finds the correct function that is called by the object pointer or reference at the time the program runs.

Dynamic binding principle: a virtual function table (an array of pointers) is built for a function class containing virtual types, and a virtual function is stored in the table, and when the class calls the constructor, at least one virtual pointer to the virtual function table is generated for each object, and when the object of this class calls a virtual function, it points to the virtual table The virtual function address of the polygon to correctly call the function.

Three. Conditions required for polymorphism.

1> to have inheritance

Coverage of the 2> function

3> to have a virtual function

4> a reference to a base class pointer or base class to a derived class object

On the code:

Class a{private:    int a;public:    a (int i): A (i) {}     virtual void print () {        cout << "A=" <<a<<endl;    }    int get_a () {  return a; }};class b{private:    int b;public:     B (int j): B (j) {}    virtual void print () {         cout<< "b=" <<b<<endl;    }    int  get_b () { return b; }};class c : public a,public b{private:     int c;public:    c (int i,int j,int k): A (i), B (j) {  c=k; }    virtual void print () {         a::p rint ();  &nbsP;      b::p rint ();        cout<< " C= "<<c<<endl;    }    void get_ab () { cout< <get_a () << " " <<get_b () <<endl; }};

#include <iostream> #include "muti_inheritance.h" int main (int argc, const char * argv[]) {//Insert code here ...    C x (5,8,10);    A *ap = &x;   A pointer to the Class C object Ap->print ();  Print in output Class A (implemented by dynamic bindings) X.A::p rint ();    Print X.get_ab () for output Class A;    (rewrite) Call Class C of Get_ab () std::cout << "Hello, world!\n"; return 0;}

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Polymorphism in C + +