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類有指針成員時(shí)的處理（1）拷貝時(shí)復(fù)制指針

#include <cstdlib>

#include <iostream>

using namespace std;

class u_ptr

{

friend class Foo1;

private:

u_ptr(int* pp):p(pp),usecount(1){cout<<"u_ptr construction\n";}

private:

int usecount;

int *p;

};

class Foo1

{

public:

Foo1(int* pp, int vv):p(new u_ptr(pp)),val(vv){cout<<"Foo construction\n";}

Foo1(const Foo1& other){ p = other.p; val=other.val; p->usecount++;cout<<"Foo1 copy"<<p->usecount<<"\n";}

Foo1& operator=(Foo1& rhs){ rhs.p->usecount++; if(--(p->usecount)==0){cout<<"delete p"<<endl; delete p;} p = rhs.p; val=rhs.val;cout<<"Foo1 assign"<<p->usecount<<"\n"; return *this;}

~Foo1(){ if(--(p->usecount)==0) delete p;cout<<"Foo1 destruction"<<p->usecount<<"\n";}

private:

u_ptr *p;

int val;

};

int main()

{

int a=9,b=10;

int* p=&a;

int* pp=&b;

Foo1 f(p,a);

Foo1 f2(f);

Foo1 f3(pp,b);

f3=f2;

return 0;

}

為了看清楚指針指向，改為public

#include <cstdlib>

#include <iostream>

using namespace std;

class u_ptr

{

friend class Foo1;

private:

u_ptr(int* pp):p(pp),usecount(1){cout<<"u_ptr construction\n";}

public:

int usecount;

int *p;

};

class Foo1

{

public:

Foo1(int* pp, int vv):p(new u_ptr(pp)),val(vv){cout<<"Foo construction\n";}

Foo1(const Foo1& other){ p = other.p; val=other.val; p->usecount++;cout<<"Foo1 copy"<<p->usecount<<"\n";}

Foo1& operator=(Foo1& rhs){ rhs.p->usecount++; if(--(p->usecount)==0){cout<<"delete p"<<endl; delete p;} p = rhs.p; val=rhs.val;cout<<"Foo1 assign"<<p->usecount<<"\n"; return *this;}

~Foo1(){ if(--(p->usecount)==0) delete p;cout<<"Foo1 destruction"<<p->usecount<<"\n";}

void show(){cout<<*(p->p)<<' '<<val<<endl;}

public:

u_ptr *p;

int val;

};

int main()

{

int a=9,b=10;

int* p=&a;

int* pp=&b;

Foo1 f(p,a);

Foo1 f2(f);

Foo1 f3(pp,b);

f3 = f2;

f.show();f2.show();f3.show();

(*f.p->p)++;

f.show();f2.show();f3.show();

return 0;

}

posted on 2010-05-08 13:32 elprup 閱讀(242) 評(píng)論(0) 編輯收藏引用所屬分類: c++實(shí)例

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