理解和使用C++中的智能指针

           使用C++一个最大的好处是它的动态性。我们可以使用new ,delete 动态分配内存和释放内存。但是有时候就会出现一些问题，如果我们忘记删除用new创建的对象，将会出现内存泄露，在长期运行的系统中，甚至一个很小的内存泄露将会造成很大的问题。所以，怎么样保证每一个new对应一个delete呢？

          一个很好的办法是用C++中的auto_ptr变量。接下来讲使用智能指针来解决这个问题。 在MyAuto_Ptr类中实现智能指针，用类

MyTestObect 测试智能指针。

测试类：MyTestObect

class MyTestObject{    string name;    int age;public:    MyTestObject(string s, int a)    {        name = s;        age = a;        cout << "Object created\n";    }    ~MyTestObject(void)    {        cout << "Object destroyed\n";    }    string GetName()    {        return name;    }    int GetAge()    {        return age;    }};

智能指针类：MyAuto_Ptr

获取指针

template <class T>class MyAuto_Ptr{private:    T *ptr;public:    //构造函数    explicit MyAuto_Ptr(T *p = 0)        :ptr(p)    {    }    //析构函数    ~MyAuto_Ptr(void)    {         delete ptr;    }    //复制构造函数    MyAuto_Ptr(MyAuto_Ptr<T> &source)    {        ptr = source.ptr;        //Since the ownership gets transferred lets point the source to 0        source.ptr = 0;    }    MyAuto_Ptr& operator=(MyAuto_Ptr<T> &source)    {        //check for self reference        if(ptr != source.ptr)        {            //flush the existing memory            delete ptr;            ptr = 0;            // use the new pointer            ptr = source.ptr;            //Since the ownership gets transferred lets point the source to 0            source.ptr = 0;            return *this;        }    }    //获取指针    T& operator *()    {        return *ptr;    }    //    T* operator ->()    {        return ptr;    }    //获取指针的值    T* get()    {        return ptr;    }    //重设指针的值    void reset(T *newVal)    {        delete ptr;        ptr = newVal;    }    //release the pointer and returns the ownership    T* release()    {        T *t = ptr;        ptr = 0;        return t;    }};

测试代码：

int main(int argc, char* argv[]){    {//dummy brace to test the destruction        MyAuto_Ptr<MyTestObject> p(new MyTestObject("Rahul Singh", 29));        //test the -> operator        cout << "Name: " << p->GetName() << ", Age: " << p->GetAge() << "\n";        //test the transfer of ownership in copy constructor        MyAuto_Ptr<MyTestObject> p2(p);        //test the * operator        cout << "Name: " << (*p2).GetName() << ", Age: " << (*p2).GetAge() << "\n";        //test the transfer of ownership in assignment operator        MyAuto_Ptr<MyTestObject> p3;        p3 = p2;        //test the get function        cout << "Name: " << p3.get()->GetName() << ",            Age: " << p3.get()->GetAge() << "\n";        //lets test the reset function        p3.reset(new MyTestObject("Megha Singh", 28));        //test the get function        cout << "Name: " << p3.get()->GetName() << ",            Age: " << p3.get()->GetAge() << "\n";        //finally lets test the release function        MyAuto_Ptr<MyTestObject> p4(p3.release());        cout << "Name: " << p4.get()->GetName() << ",            Age: " << p4.get()->GetAge() << "\n";    }    getchar();    return 0;}

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