When you want an object to behave like a pointer, you usually use operator - >

Pointer indirect reference operator must be a member function

The pointer indirect reference operator has a limitation: it must return an object that also has a pointer indirect
Reference operator, or must return a pointer, used to select a pointer indirect reference operator arrow
What to point to

 

//: C12:SmartPointer.cpp
// From Thinking in C++, 2nd Edition
// Available at http://www.BruceEckel.com
// (c) Bruce Eckel 2000
// Copyright notice in Copyright.txt
#include <iostream>
#include <vector>
#include "../require.h"
using namespace std;

class Obj {
  static int i, j;
public:
  void f() const { cout << i++ << endl; }
  void g() const { cout << j++ << endl; }
};

// Static member definitions:
int Obj::i = 47;
int Obj::j = 11;

// Container:
class ObjContainer {
  vector<Obj*> a;
public:
  void add(Obj* obj) { a.push_back(obj); }
  friend class SmartPointer;
};

class SmartPointer {
  ObjContainer& oc;
  int index;
public:
  SmartPointer(ObjContainer& objc) : oc(objc) {
    index = 0;
  }
  // Return value indicates end of list:
  bool operator++() { // Prefix
    if(index >= oc.a.size()) return false;
    if(oc.a[++index] == 0) return false;
    return true;
  }
  bool operator++(int) { // Postfix
    return operator++(); // Use prefix version
  }
  Obj* operator->() const {
    require(oc.a[index] != 0, "Zero value "
      "returned by SmartPointer::operator->()");
    return oc.a[index];
  }
};

int main() {
  const int sz = 10;
  Obj o[sz];
  ObjContainer oc;
  for(int i = 0; i < sz; i++)
    oc.add(&o[i]); // Fill it up
  SmartPointer sp(oc); // Create an iterator
  do {
    sp->f(); // Pointer dereference operator call
    sp->g();
  } while(sp++);
  getchar();
} ///:~

 

Class Obj defines some objects used in the program

In main(), once the Obj object is loaded into the container oc, the SP of a SmartPointer class is created

The underlying mechanism of pointer indirect operators is more complex than other operators, but the purpose is the same. It is a class
More convenient syntax for

output
47
11
48
12
49
13
50
14
51
15
52
16
53
17
54
18
55
19
56
20

Program exception after