question1 赋值运算操作符

注意的问题书上讲的很详细了

下面是代码实现，但是VS有一个问题，strcpy安全性较低，虽然可以通脱编译，但是运行会报错，提示用strcpy_s()替代，但是，这里用strcpy()替代也不行，

//题目：如下为类型CMyString的声明，请为该类型添加赋值运算符
//以下为完整代码和测试用例
#pragma warning(disable:4996)
#include <iostream>
#include <cstring>
using namespace std;
class CMyString {
public:
    CMyString(char* pData = nullptr);
    CMyString(const CMyString& str);
    ~CMyString(void);
    // operator "="
    CMyString& operator =(const CMyString& str);
    void print();//用来输出测试结果
private:
    char*m_pData;
};

//the defination of the constructor fun
CMyString::CMyString(char* pData)
{
    if (pData == nullptr)
        m_pData = new char[1];
    m_pData[0] = '';
}

CMyString::CMyString(const CMyString& str)
{
    int len = strlen(str.m_pData);
    m_pData = new char[len + 1];
    //m_pData(str.m_pData);
    strcpy(m_pData, str.m_pData);
    
}

CMyString::~CMyString()
{
    //delete m_pData[];
    delete[]m_pData;
}

CMyString& CMyString:: operator =(const CMyString &str)
{
    if (this == &str);
    return *this;
    
    delete[]m_pData;
    m_pData = nullptr;

    m_pData = new char[strlen(str.m_pData) + 1];
    strcpy(m_pData, str.m_pData);
    return *this;
    
}

void CMyString:: print()
{
    cout << m_pData << endl;
}
//测试用例

void test1()
{
    char* str = "Hello World!";
    CMyString str1(str);
    CMyString str2;
    str2 = str1;//call CMystring& operator=(const CMyString& str)
    cout << " str is : " << str << endl;
    //cout << "str2 is : " << str2.print() << endl;//没有重载<<运算符，还不能用
    cout << "after 赋值" <<"str2 is : "<< endl;
    str2.print();
 }

void test2()//赋值给自己
{
    char* str = "Hello world!";
    CMyString str1(str);
    str1=str1;
    cout << " str is : " << str << endl;
    
    cout << "after 赋值" << "str1 is : " << endl;
    str1.print();

}

void test3()//连续赋值
{
    char* str = "Hello World!";
    CMyString str1(str);
    CMyString str2, str3;
    str3 = str2 = str1;
    cout << "str1 is : " << endl;
    str1.print();
    cout << "str2 is : " << endl;

    str2.print();
    cout << "str3 is : " << endl;
    str3.print();
}


int main()
{
    test1();
    test2();
    test3();
    system("pause");
    return 0;
}