KwCheng's blog

#include <string>
using namespace std;

class Ball { 
public: 
    Ball(); 
    Ball(double, const char*); 
    Ball(double, string&); 
 
    double radius() {
        return _radius;
    }
 
    string& name() {
        return _name; 
    }
 
    void radius(double radius) {
        _radius = radius;
    } 
 
    void name(const char *name) {
        _name = name;
    }
 
    void name(string& name) {
        _name = name;
    }
 
    double volumn() {
        return (4 / 3 * 3.14159 * _radius * _radius * _radius); 
    }
 
private:
    double _radius; // 半徑 
    string _name; // 名稱 
};

When we create two objects likes b1(1, "RBall")與b2(2, "GBall") , 

although their data member are individual , but the member function are the same.

so , how does the member function know which function call him?

The answer is this pointer , this pointer can help us deal with this problem.

when you call name() method , the content actually is " return this->_name " ,

this pointer stores address of b1 if the object b1 call the method , 

it is the same situation , if the object b2 call the method , this pointer will store address of object b2.

ref : http://caterpillar.onlyfun.net/Gossip/CppGossip/thisPointer.html