C++ 深拷贝与浅拷贝

浅拷贝

Array.h

class Array{
public:
Array();
Array(const Array& arr);
~Array();
void setCount(int c);
int getCount();
private:
int m_iCount;
};


Array.cpp
#include <iostream>
#include "Array.h"
using namespace std;

Array::Array()
{
cout << "Array" << endl;
}

Array::Array(const Array& arr)
{
m_iCount = arr.m_iCount;
cout << "Array&" << endl;
}

Array::~Array()
{
cout << "~Array" << endl;
}

void Array::setCount(int c)
{
m_iCount = c;
}

int Array::getCount()
{
return m_iCount;
}


main.cpp
#include <iostream>
#include <string>
#include "Array.h"
using namespace std;

int main() {

Array arr1;
arr1.setCount(5);

Array arr2(arr1);

cout << arr2.getCount() << endl;
return 0;
}


浅拷贝可能带来的错误
Array.hclass Array{
public:
Array(int c);
Array(const Array& arr);
~Array();
void setCount(int c);
int getCount();
void printAddr();
private:
int m_iCount;
int *m_pArr;
};Array.cpp
#include <iostream>
#include "Array.h"
using namespace std;

Array::Array(int c)
{
m_iCount = c;
m_pArr = new int[m_iCount];
cout << "Array" << endl;
}

Array::Array(const Array& arr)
{
m_pArr = arr.m_pArr;
m_iCount = arr.m_iCount;
cout << "Array&" << endl;
}

Array::~Array()
{
delete []m_pArr;
m_pArr = NULL;
cout << "~Array" << endl;
}

void Array::setCount(int c)
{
m_iCount = c;
}

int Array::getCount()
{
return m_iCount;
}

void Array::printAddr()
{
cout << m_pArr << endl;
}


main.cpp
#include <iostream>
#include <string>
#include "Array.h"
using namespace std;

int main() {

Array arr1(5);
//arr1.setCount(5);

Array arr2(arr1);

cout << arr2.getCount() << endl;
return 0;
}

结束时出错，因为arr1和arr2中的m_parr都指向一块内存，而两个对象的析构函数被调用的时候要释放两次一样的内存，所以会造成系统崩溃。

深拷贝

Array.cpp

#include <iostream>
#include "Array.h"
using namespace std;

Array::Array(int c)
{
m_iCount = c;
m_pArr = new int[m_iCount];
for (int i = 0; i < m_iCount; i++) {
m_pArr[i] = i;
}
cout << "Array" << endl;
}

Array::Array(const Array& arr)
{
m_iCount = arr.m_iCount;
m_pArr = new int[m_iCount];
for (int i = 0; i < m_iCount; i++) {
m_pArr[i] = arr.m_pArr[i];
}
cout << "Array&" << endl;
}

Array::~Array()
{
delete []m_pArr;
m_pArr = NULL;
cout << "~Array" << endl;
}

void Array::setCount(int c)
{
m_iCount = c;
}

int Array::getCount()
{
return m_iCount;
}

void Array::printAddr()
{
cout << m_pArr << endl;
}