Hello Experts!
I have one class template here called Handle and one concrete class called
Point.
At the bottom is the main program and the class template definitions for
Handle.
This program works fine but there are two thing that I
don't understand completely and that is these two operator that exist in the
class template Handle.
Body* operator->()
{ return bridge; }
Body& operator*()
{ return *bridge; }
How can it be possible to use this line cout << hp1->getX() << endl;
when hp1 is not a pointer. I instansiate this hp1 in main that exist at the
bottom.
And the same here how can it be possible to dereference object hp1
when hp1 is not a pointer.
Point b = *hp1;
The second question is the operator->() returns a pointer so the statement
hp1-> will return a pointer to
Body by calling the operator->() how is it then possible to call getX(). If
I substitute this it's look like.
hp1.operator->()getX
Note you have no -> before getX. Because this program works there must exist
a -> before getX but I can't understand how these two characters -> can be
placed there.
********************
class definition for Handle
********************
template <typename Body>
class Handle
{
public:
explicit Handle(Body* b = 0) : bridge(b), counter(new int(1))
{ }
Handle(const Handle<Body>& h) :counter(h.counter)
{ (*counter)++; }
~Handle()
{
if (--(*counter) == 0)
{
delete counter;
delete bridge;
}
}
Handle& operator=(const Handle<Body>& rhs)
{
if (this == &rhs || bridge == rhs.bridge)
return *this;
if (--(*counter) == 0)
{
delete counter;
delete bridge;
}
bridge = rhs.bridge;
counter = rhs.counter;
(*counter)++;
return *this;
}
Body* operator->()
{ return bridge; }
Body& operator*()
{ return *bridge; }
private:
Body* bridge;
int* counter;
};
class Point
{
public:
Point(double d1=0, double d2=0) : x(d1), y(d2) {}
virtual ~Point() {}
double getX()
{ return x; }
double getY()
{ return y; }
void setX(double d)
{ x = d; }
void setY(double d)
{ y = d; }
private:
double x;
double y;
};
#include <iostream>
#include "handle.h"
using namespace std;
int main()
{
Handle<Point> hp1(new Point(1,2));
cout << hp1->getX() << endl;
Point b = *hp1;
Handle<Point> hp2(hp1);
Handle<Point> hp3(new Point(3,4));
hp3 = hp2;
cout << hp2->getY() << " " << hp3->getY() << endl;
return 0;
}
Many thanks
//Tony
