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C++ Programming for Experienced Engineers

Pointer to Member Operators

Explore how to use C++ pointer to member operators .* and ->* for accessing members of structures. Understand their syntax, how they refer to class offsets rather than object addresses, and see examples of accessing multiple object elements using these pointers.

We'll cover the following...

Problem

Write a program to access the struct members using the pointer to member operators .* and ->*.

Sample run

Here’s what you should see when you run the program.

10      3.14
10      3.14
20      6.28
20      6.28
30      9.22
40      7.33
60      8.88

Coding solution

Here is a solution to the problem above.

C++
// Pointer to member operators
#include <iostream> 
struct sample 
{ 	
	int a ; 	
	float b ; 
} ;  
int main( ) 
{ 	
	sample so = { 10, 3.14f } ;
	
	int sample::*p1 = &sample::a ; 	
	float sample::*p2 = &sample::b ; 
	
	std :: cout << so.*p1 << "\t" << so.*p2 << std :: endl ;
	sample *sp ;
	sp = &so ;
	std :: cout << sp->*p1 << "\t" << sp->*p2 << std :: endl ;
	// we can even assign new values
	so.*p1 = 20 ;
	sp->*p2 = 6.28f ;
	std :: cout << so.*p1 << "\t" << so.*p2 << std :: endl ;
	std :: cout << sp->*p1 << "\t" << sp->*p2 << std :: endl ;
	sample soarr[ ] = {
		{ 30, 9.22f },
		{ 40, 7.33f },
		{ 60, 8.88f } 
		} ;
	for ( int i =0 ; i <= 2 ; i++ ) 		
		std :: cout << soarr[ i ].*p1 << "\t" << soarr[ i ].*p2 << std :: endl ;
	
	return 0 ; 
}

Explanation

To carry out the access and the ...