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[];
     m_pData[] = '\0';
 }

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