C++基础——深拷贝，浅拷贝，智能指针

1.浅拷贝

　　简单的赋值拷贝操作

 

　　

2.深拷贝

　　在堆区重新申请空间，进行拷贝操作

　　

class Person {
public:
    //无参（默认）构造函数
    Person() {
        cout << "无参构造函数!" << endl;
    }
    //有参构造函数
    Person(int age ,int height) {
        
        cout << "有参构造函数!" << endl;

        m_age = age;
        m_height = new int(height);
        
    }
    //拷贝构造函数  
    Person(const Person& p) {
        cout << "拷贝构造函数!" << endl;
        //如果不利用深拷贝在堆区创建新内存，会导致浅拷贝带来的重复释放堆区问题
        m_age = p.m_age;
        m_height = new int(*p.m_height);
        
    }

    //析构函数
    ~Person() {
        cout << "析构函数!" << endl;
        if (m_height != NULL)
        {
            delete m_height;
        }
    }
public:
    int m_age;
    int* m_height;
};

void test01()
{
    Person p1(18, 180);

    Person p2(p1);

    cout << "p1的年龄： " << p1.m_age << " 身高： " << *p1.m_height << endl;

    cout << "p2的年龄： " << p2.m_age << " 身高： " << *p2.m_height << endl;
}

int main() {

    test01();

    system("pause");

    return 0;
}

3.智能指针

#pragma once
class Smart_ptr
{
    friend class ChasPtr;

private:
    int* ip;
    size_t use;    //计数
    Smart_ptr(int *p):ip(p),use(1){}
    ~Smart_ptr()
    {
        delete ip;
    }
};

class ChasPtr {



public:

    ChasPtr(int *p,int i):ptr(new Smart_ptr(p)),val(i){}

    ChasPtr(const ChasPtr& orig) :ptr(orig.ptr), val(orig.val)
    {
        ++ptr->use;
    }
    int* get_ptr()const { return ptr->ip; };
    int get_int()const { return val; }

    void set_ptr(int* p) { ptr->ip = p; };
    void set_int(int i) { val = i; };

    int get_ptr_val()const { return *ptr->ip; };
    void set_ptr_val(int val)const { *ptr->ip = val; };



    ChasPtr& operator=(const ChasPtr&);

    ~ChasPtr()
    {
        if (ptr->use-- == 0) delete ptr;
    }

private:
    //int* ptr;
    Smart_ptr* ptr;
    int val;
};

ChasPtr& ChasPtr::operator=(const ChasPtr&rhs)
{
    ++rhs.ptr->use;
    if (--ptr->use == 0) delete ptr;

    ptr = rhs.ptr;
    val = rhs.val;

    return *this;
}

    int obj = 1;
    ChasPtr ptr1(&obj, 42);
    ChasPtr ptr2(ptr1);

    cout << ptr1.get_ptr_val() << " , " << ptr1.get_int() << endl;
    cout << ptr2.get_ptr_val() << " , " << ptr2.get_int() << endl;

    ptr2.set_ptr_val(10);
    ptr2.set_int(50);
    cout << ptr1.get_ptr_val() << " , " << ptr1.get_int() << endl;
    cout << ptr2.get_ptr_val() << " , " << ptr2.get_int() << endl;