剑指offer——赋值运算符函数

#include<iostream>using namespace std;class String{public:    String(char * pData = NULL);    String(const String& str);    ~String();    String& operator=(const String& str);    void print();private:    char * m_pData;};String::String(char * pData){    if (pData == NULL)    {        m_pData = new char[1];        m_pData[0] = '\0';    }    else    {        int length = strlen(pData);        m_pData = new char[length + 1];        strcpy(m_pData, pData);    }}String::String(const String& str){    int length = strlen(str.m_pData);    m_pData = new char[length + 1];    strcpy(m_pData, str.m_pData);}String::~String(){    delete[] m_pData;}/*//常规方法String& String::operator=(const String& str){    if (this == &str)        return *this;    delete[] m_pData;    m_pData = NULL;    m_pData = new char[strlen(str.m_pData) + 1];    strcpy(m_pData, str.m_pData);    return *this;}*//*//先分配，再释放String& String::operator=(const String& str){    if (this == &str)        return *this;    char * temp = new char[strlen(str.m_pData) + 1];;    delete[] m_pData;    m_pData = temp;    strcpy(m_pData, str.m_pData);    return *this;}*///创建临时变量String& String::operator=(const String& str){    if (this == &str)        return *this;    String ss(str);    char * temp = ss.m_pData;    ss.m_pData = m_pData;    m_pData = temp;    return *this;}//测试代码void String::print(){    cout << m_pData << endl;}void Test1(){    cout << "Test1 begins:\n";    char * text = "hello world";    String str1(text);    String str2;    str2 = str1;    cout << "The expected result is: " << text << endl;    cout << "The actual result is:";    str2.print();    cout << endl;}//赋值给自己void Test2(){    cout << "Test1 begins:\n";    char * text = "hello world";    String str1(text);    str1 = str1;    cout << "The expected result is: " << text << endl;    cout << "The actual result is:";    str1.print();    cout << endl;}//连续赋值void Test3(){    cout << "Test1 begins:\n";    char * text = "hello world";    String str1(text);    String str2, str3;    str3 = str2 = str1;    cout << "The expected result is: " << text << endl;    cout << "The actual result is:";    str2.print();    cout << endl;    cout << "The expected result is: " << text << endl;    cout << "The actual result is:";    str3.print();    cout << endl;}int main(){    Test1();    Test2();    Test3();    return 0;}