重写String类

classs String

{

    private:

    char *m_data;   //数据成员

 

    public:

    String(const char *str = NULL)    //普通构造函数

    {

         if (str == NULL)

         {

             m_data = new char[1];

             *m_data = '\0';

         }

         else

         {

             int len = strlen(str);

             m_data = new char[len+1];

             strcpy(m_data, str);

         }

    }

 

    ~String()    //析构函数

    {

         delete []m_data; 

         m_data = NULL;

    }  

 

    String(const String &other)    //拷贝构造函数

    {

         int len = strlen(other.m_data);

         m_data = new char[len + 1];

         strcpy(m_data, other.m_data);

    }

 

    String& operate=(const String &other)    //赋值函数

    {

         if (&other == this)

         {

              return *this;

         }

         else

         {

              delete []m_data;

              m_data = NULL;

              int len = strlen(other.m_data);

              m_data  = new char[len+1];

              strcpy(m_data, other.m_data);

              return *this;

         }

    }

};