剑指offer-0x01

赋值运算函数

对于定义一个赋值运算符函数时，需要注意一下几点：

函数的返回类型必须是一个引用，因为只有返回引用，才可以连续赋值

传入的参数声明为常量引用，可以提高代码效率，同时赋值运算函数内不会改变传入的实例状态

一定要记得释放实例自身已有的内存，否则程序容易出现内存泄露

注意传入的参数和当前的实例是不是同一个实例，如果是同一个，则不用进行赋值操作，直接返回即可

自己的代码 求鄙视

//main.h#ifndef MAIN_H_INCLUDED#define MAIN_H_INCLUDEDclass CMyString{public:    CMyString(char* pData = NULL);    CMyString(const CMyString & str);    char* getStr();    ~CMyString();    CMyString& operator = (const CMyString &str);private:    char* m_pdata;};#endif // MAIN_H_INCLUDED

//main.cpp#include <iostream>#include <cstring>#include "main.h"//must use "" not <>using namespace std;CMyString& CMyString::operator = (const CMyString &str){    if (this == &str)        return *this;//if itself = itself then return directly        //in case delete itself when delete        delete []m_pdata;        m_pdata = NULL;        m_pdata = new char[strlen(str.m_pdata)+1];        strcpy(m_pdata,str.m_pdata);        return *this;//return a value}char* CMyString::getStr(){    return m_pdata;}CMyString::CMyString(char* pData){    int length = strlen(pData);        m_pdata = new char[length+1];        strcpy(m_pdata,pData);}CMyString::~CMyString(){    delete []m_pdata;}int main(){    CMyString str("i love china!");    CMyString str1;    str1 = str;    cout<<str1.getStr()<<endl;    cout << "Hello world!" << endl;    return 0;}E:\CodeBlocks\operator\main.h|14|error: 'char* CMyString::m_pdata' is private|

别人的代码

#include<iostream>#include<cstring>using namespace std;class CMyString{public:    CMyString(char *pData=NULL);    CMyString(CMyString &str);    CMyString& operator=(CMyString &str);    ~CMyString(void);    void Print(){ cout << m_pData; }private:    char* m_pData;};CMyString::CMyString(char *pData){    if (NULL == pData)    {        m_pData = NULL;        return;    }    else    {        unsigned int len = strlen(pData)+1;        m_pData = new char[len];        for (int i = 0; i < len; i++)            m_pData[i] = pData[i];        m_pData[len] = '\0';    }}CMyString::CMyString(CMyString &str){    unsigned int len = strlen(str.m_pData) + 1;    m_pData = new char[len];    for (int i = 0; i < len; i++)        m_pData[i] = str.m_pData[i];    m_pData[len] = '\0';}CMyString & CMyString::operator=(CMyString &str){    if (this == &str)        return *this;    else    {        unsigned int len = strlen(str.m_pData) + 1;        char *pTemp = new char[len];        for (int i = 0; i < len; i++)            pTemp[i] = str.m_pData[i];        pTemp[len] = '\0';        delete[]m_pData;//出错！！！不解        m_pData = pTemp;    }    return *this;}CMyString::~CMyString(){    delete [] m_pData;}int main(){    char c1[10] = "majunfu";    CMyString s1(c1);    CMyString s2 = s1;    s1 = s2;    s1.Print();    s2.Print();    return 0;}