, new, , delete. , , , . , , . , . , .
#include "iostream.h"
#include "string.h"
template <class T>
struct Status //
{ T *RealPtr; //
int Count; //
};
template <class T>
class Point // -
{ Status<T> *StatPtr;
public:
Point(T *ptr=0); //
Point(const Point &); //
~Point();
Point &operator=(const Point &); //
// Point &operator=(T *ptr); //
T *operator->() const;
T &operator*() const;
};
Point . NULL, Status, , NULL. Status
template <class T>
Point<T>::Point(T *ptr) //
{ if(!ptr) StatPtr=NULL;
else
{ StatPtr=new Status<T>;
StatPtr->RealPtr=ptr;
StatPtr->Count=1;
}
}
StatPtr , , .
template <class T> //
Point<T>::Point(const Point &p):StatPtr(p.StatPtr)
{
if(StatPtr) StatPtr->Count++; //
}
1, 0
template <class T>
Point<T>::~Point() //
{ if(StatPtr)
{ StatPtr->Count--; //
if(StatPtr->Count<=0) // <=0,
{ delete StatPtr->RealPtr; //
delete StatPtr;
}
}
}
template <class T>
T *Point<T>::operator->() const
{ if(StatPtr) return StatPtr->RealPtr;
else return NULL;
}
template <class T>
T &Point<T>::operator*() const // StatPtr
{ if(StatPtr) return *StatPtr->RealPtr; // this-
else throw bad_pointer; //
}
= , =.
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|
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template <class T>
Point<T> &Point<T>::operator=(const Point &p)
{ // =
if(StatPtr)
{ StatPtr->Count--;
if(StatPtr->Count<=0) //
{ delete StatPtr->RealPtr; //
delete StatPtr; //
}
}
//
StatPtr=p.StatPtr;
if(StatPtr) StatPtr->Count++;
return *this;
}
Struct Str
{ int a;
char c;
};
void main()
{ Point<Str> pt1(new Str); // Point,
// pt1,
// - Str, -
//
Point<Str> pt2=pt1,pt3; // pt2 ,
// pt3
pt3=pt1; // pt3 pt1
(*pt1).a=12; // operator*() this pt1
(*pt1).c='b';
int X=pt1->a; // operator->() this- pt1
char C=pt1->c;
}
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2. [1,2,3,4,5].
3. .
4. , .
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2. . \ . >, < . .
3. . . .
4. . . .
