copy构造函数使用深copy_默认copy构造-优快云博客

本文链接：https://blog.youkuaiyun.com/andrewgithub/article/details/108433874

本文深入探讨了C++中深拷贝构造函数的实现原理，通过具体代码示例展示了如何为自定义类编写深拷贝构造函数，以避免浅拷贝带来的问题。文章详细解释了在对象初始化和赋值过程中深拷贝构造函数的调用时机。

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=操作符的默认copy构造函数是浅copy，要是想使用深copy需要编写copy构造函数，编写深copy构造函数的形式如下,调用方式除了显示的调用，当首次定义对象，并使用=进行对象初始化的时候也会调用该copy构造函数 Array a2 = a1;

Array::Array(const Array& obj)
{
  this->m_length = obj.m_length;
  this->m_space = new int[this->m_length]; //分配内存空间

  for (int i=0; i<m_length; i++) //数组元素复制
  {
  	this->m_space[i] = obj.m_space[i];
  }
}


#include "myarray.h"

//

//int m_length;
//char *m_space;
Array::Array(int length)
{
	if (length < 0)
	{
		length = 0; //
	}

	m_length = length;
	m_space = new int[m_length];
}

//Array a2 = a1;
// 当首次定义对象并调用 = 操作符的时候，调用该深copy构造函数，其他时候的 =就是=操作符
Array::Array(const Array& obj)
{
	this->m_length = obj.m_length;
	this->m_space = new int[this->m_length]; //分配内存空间

	for (int i=0; i<m_length; i++) //数组元素复制
	{
		this->m_space[i] = obj.m_space[i];
	}
}
Array::~Array()
{
	if (m_space != NULL)
	{
		delete[] m_space;
		m_space = NULL;
		m_length = -1;
	}
}

//a1.setData(i, i);
void Array::setData(int index, int valude)
{
	m_space[index] = valude;
}
int Array::getData(int index)
{
	return m_space[index];
}
int Array::length()
{
	return m_length;
}

test.cpp函数

#include <iostream>

using namespace std;


class TestCopy
{
private:
    /* data */
    int legth;
    int *pArray;
public:
    TestCopy(int len);
    ~TestCopy();
    // TestCopy t2 = t1;  特殊构造函数   当首次定义t2并调用=的时候，就会调用该构造函数
    TestCopy(TestCopy & test);
    int setArray(int index, int valued);
    int getLength(void);
    int printArray(int index);
};

TestCopy::TestCopy(int len)
{
    if(len < 0)
    {
        len = 0;
    }

    legth = len;
    pArray = new int[len];

}

TestCopy::~TestCopy()
{
        if(pArray != NULL)
        {
            delete[] pArray;
            legth = -1;
        }
}

TestCopy::TestCopy(TestCopy & test)
{
    this->legth = test.legth;
    this->pArray = new int[this->legth];

    for (int i = 0; i < this->legth; i++)
    {
        this->pArray[i] = test.pArray[i];
    }
    cout << "construct function is called"  << endl;
}


int TestCopy::setArray(int index, int valued)
{
    this->pArray[index] = valued;
    return 0;
}


int TestCopy::getLength(void)
{
    return this->legth;
}


int TestCopy::printArray(int index)
{
    cout << this->pArray[index] << endl;
    return 0;
}

int main(int argc, const char** argv) 
{    
    
    TestCopy t1(10);
    
    for(int i = 0; i < t1.getLength(); i ++)
    {
        t1.setArray(i, i);
    }

    // 开始调用构造函数
    cout << "---------------------start-----------------" << endl;

    TestCopy t2 = t1;

    cout << "----------------------end------------------" << endl;
    for(int i = 0; i  < t2.getLength(); i++)
    {
        t2.printArray(i);
    }

    
    
    
    return 0;
}

输出结果：

$ ./a.out 
---------------------start-----------------
construct function is called
----------------------end------------------
0
1
2
3
4
5
6
7
8
9