#include <iostream>

#include<string.h>

using namespace std;

class String

{

    int length;

    int i;

private:

    char* m_data;//用于保护字符串

public:

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

    {

        cout<<"调用了构造函数"<<endl;

        if(str==NULL)

        {

            length=;

            m_data=new char();   //指针指向这段空间

            m_data[]='\0';

        }

        else

            length=strlen(str);

            m_data=new char(length+);

            strcpy(m_data, str);

    }

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

    {

        cout<<"调用了拷贝函数"<<endl;

        if(m_data)

        {

            delete []m_data;

            int length=strlen(other.m_data);

            m_data=new char[length+];

            strcpy(m_data, other.m_data);

            }

    }

    ~String(void)//析构函数

    {

        cout<<"调用了析构函数"<<endl;

        if (m_data) {

            delete []m_data;

        }

    }

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

    {

        cout<<"调用了赋值函数"<<endl;

        if (this==&other)                  //检查自赋值

            return *this;

            delete []m_data;

            int length=strlen(other.m_data);

            m_data=new char[length+];

            strcpy(m_data, other.m_data);

            return *this;

    }

};

int main()

{

    String str("abc");

    String str1(str);

    str.operator=(str);

}