C ++ references pointer virtual functions

In the past, I did not pay much attention to the reference subclass or base class pointer pointing to the subclass in C ++ inheritance. Now, write a small program to test this result.

// Testcpp. cpp: defines the entry point for the console application.

# Include "stdafx. H"
# Include "iostream"
Using namespace STD;

Class B
{
Public:
Virtual void print ()
{
Cout <"This is B" <Endl;
}
};

Class A: Public B // Class A inherits Class B
{
Public:
Virtual void print ()
{
Cout <"this is a" <Endl;
}
};

Int _ tmain (INT argc, _ tchar * argv [])
{

A;

B;

B & b1 = A; // base class reference subclass

B * pb = & A; // The base class Pointer Points to the subclass.

Cout <"A. Print ():";

A. Print ();

Cout <"B. Print ():";

B. Print ();

B =;

Cout <"B = a B. Print :";

B. Print ();

 

Cout <"b1.print ():";

B1.print ();

Cout <"Pb-> Print ():";

Pb-> Print ();

Getchar ();

Return 0;

}

The output result is as follows:

A. Print (): This is

B. Print (): This is B

B = a B. Print: This is B

B1.print (): This is

Pb-> Print (): This is

First, I start from inheritance, because a inherits B. For example:

Note: The virtual function pointer is a hidden member variable. This Hidden variable does not change in the copy constructor.

Analyze the following statements:

B = A; // use object A to construct function B. In this process, only the copy constructor is called to assign values to data members, therefore, the virtual function pointer of object B still points to the virtual function of object B.

Cout <"B = AB. Print :";

B. Print (); // B = a B. Print: This is B

 

Cout <"b1.print ():"; // B1 is a reference, that is, another name of the memory address of object A. Therefore, B1 points to the memory address of object.

B1.print (); // b1.print (): This is

 

Cout <"Pb-> Print ():"; // the pointer actually stores the address of another memory in the memory. To put it bluntly, it is also a variable, this variable is special, that is, the Pb variable stores the address of the memory of object,

Pb-> Print (); // This Is