关于智能指针和拷贝构造函数的一个例子

zukeqiang@35fb9925ca21:~/test$ ./oz

c1:

_Creat_100

Fun(c1):

_Creat_cp_101

_Destory_98

c2:

_Creat_100

c3:

_Destory_98

_Destory_98

123 456 789

1

1

2

2

#include <iostream>

#include <memory>



using namespace std;



class B;    //声明

class A

{

public:

    shared_ptr<B> pb_;

    ~A()

    {

        cout << "A delete\n";

    }

};



class B

{

public:

    shared_ptr<A> pa_;

    ~B()

    {

        cout << "B delete\n";

    }

};



void test_w()

{

    shared_ptr<B> pb(new B());

    shared_ptr<A> pa(new A());

    cout << pb.use_count() << endl;    //1

    cout << pa.use_count() << endl;    //1

    pb->pa_ = pa;

    pa->pb_ = pb;

    cout << pb.use_count() << endl;    //2

    cout << pa.use_count() << endl;    //2

}







void test_shared()

{

    string *s1 = new string("s1");



    shared_ptr<string> ps1(s1);

    shared_ptr<string> ps2;

    cout << ps1.unique() << endl;

    cout << ps2.unique() << endl;

    ps2 = ps1;



    cout << ps1.use_count()<<endl;    //2

    cout<<ps2.use_count()<<endl;    //2

    cout << ps1.unique()<<endl;    //0



    string *s3 = new string("s3");

    shared_ptr<string> ps3(s3);



    cout << (ps1.get()) << endl;    //033AEB48

    cout << ps3.get() << endl;    //033B2C50

    cout << ps1.use_count() << endl;

    cout << ps3.use_count() << endl;

    cout << __LINE__ << "_ps1:" << *ps1 << endl;

    cout << __LINE__ << "_ps3:" << *ps3 << endl;

    cout << __LINE__ << "_ps2:" << *ps2 << endl;

    swap(ps1, ps3);    //交换所拥有的对象

    cout << (ps1.get())<<endl;    //033B2C50

    cout << ps3.get() << endl;    //033AEB48

    cout << __LINE__ << "_ps1:" << *ps1 << endl;

    cout << __LINE__ << "_ps3:" << *ps3 << endl;

    cout << ps1.use_count()<<endl;    //1

    cout << ps2.use_count() << endl;    //2

    ps2 = ps1;

    cout << __LINE__ << "_ps2:" << *ps2 << endl;

    cout << __LINE__ << "_ps1:" << *ps1 << endl;

    cout << ps1.use_count()<<endl;    //2

    cout << ps2.use_count() << endl;    //2

    ps1.reset();    //放弃ps1的拥有权，引用计数的减少

    cout << ps1.use_count()<<endl;    //0

    cout << ps2.use_count()<<endl;    //1

}





int test2()

{

    //初始化方式1

    std::unique_ptr<int> up1(new int(123));

    //初始化方式2

    std::unique_ptr<int> up2;

    up2.reset(new int(456));

    //初始化方式3 (-std=c++14)

    std::unique_ptr<int> up3 = std::make_unique<int>(789);

    cout << *up1 << " " << *up2 << " " << *up3 << endl;

}



class Complex

{

private:

    int Real;

    int Image;



public:

        ~Complex(){cout << "_Destory_" << __LINE__ << endl;}



        Complex(int r,int i):Real(r),Image(i){cout << "_Creat_" << __LINE__ << endl;}

        Complex(const Complex& c):Real(c.Real),Image(c.Image){cout << "_Creat_cp_" << __LINE__ << endl;}

};

void Fun(Complex c1)

{

}

Complex Fun2()

{

  Complex c(10,20);

  return c;

}

 

void test3()

{

        cout << "c1:" << endl;

  Complex c1(1,2);

  cout << "Fun(c1):" << endl;

  Fun(c1);

  cout << "c2:" << endl;

  Complex c2 = Fun2();

  cout << "c3:" << endl;

  Complex &c3 = c2;

  cout << "c4:" << endl;

  Complex c4 = c3;

  cout << "c5:" << endl;

  Complex c5(c4);

  cout << "c5 value:"  << endl; 

}



int main()

{

        test3();

        test2();

        test_w();

        //test_shared();

        /*

        unique_ptr<string> ps1, ps2;

        ps1 = unique_ptr<string>(new string ("Hello"));

        ps2 = move(ps1);

        ps1 = unique_ptr<string>(new string ("nihao"));

        cout << *ps2 << " " << *ps1 << endl;

        */

    return 0;

}

zukeqiang@35fb9925ca21:~/test$ ./oz

c1:

_Creat_104

Fun(c1):

_Creat_cp_105

_Destory_102

c2:

_Creat_104

c3:

c4:

_Creat_cp_105

c5:

_Creat_cp_105

c5 value:

_Destory_102

_Destory_102

_Destory_102

_Destory_102

123 456 789

1

1

2

2