类中的特殊内容

仿照string类，自己手动实现 My_string

#include <iostream>
#include <string.h>
using namespace std;

class My_string
{
private:
    int len;
    int size;
    char *ptr;
public:
    My_string():size(15),len(0)
    {
        ptr=new char[size];
        ptr[0]='\0';
    }
    My_string(const char *src)
    {
        len = strlen(src);
        ptr = new char[len+1];
        strcpy(ptr,src);
    }
    My_string(const My_string& other):ptr(new char[this->len]),len(other.len)
    {
        len = other.len;
        size = other.size;
        ptr = new char[size];
        strcpy(ptr,other.ptr);
    }
    //拷贝赋值
    My_string& operator=(const My_string& other)
    {
        if(this!=&other)
        {
            delete[]ptr;
            len = other.len;
            size = other.size;
            ptr = new char[size];
            strcpy(ptr,other.ptr);
        }
        return *this;
    }
    //析构函数
    ~My_string()
    {
        delete[]ptr;
    }
    //判空
    bool empty()
    {
        return this->len==0;
    }
    //尾插
    void push_back(char x)
    {
        if(this->len==this->size-1)
        {
            return ;
        }
        this->ptr[len++]=x;
    }
    //尾删
    void dele_back()
    {
        if(this->len==0)
        {
            return ;
        }
        this->ptr[len-1]=this->ptr[len];
        this->len--;
    }
    //at函数实现
    char &at(int x)
    {
        if(x>=0&&x<size)
        {
            return ptr[x];
        }else
        {
            cout<<"超出范围"<<endl;
            exit(1);
        }
    }
    //清空函数
    void dele_empty()
    {
        for(int i=0;i<this->len;i++)
        {
            dele_back();
        }
    }
    //返回C风格字符串
    char *my_ptr()
    {
        return this->ptr;
    }
    //返回实际长度
    int my_len()
    {
        return this->len;
    }
    //返回当前最大容量
    int my_size()
    {
        return this->size;
    }
    //二倍扩容
    void doubledilatation()
    {
        //char *ptr1=new char[size];
        //*ptr1=*this->ptr;
       // if(this->len==this->size)
       // {
      //      this->size*=2;
       // }
       // cout <<" len="<<len<<"   size="<<size<<endl;

        size *= 2;
        char *new_ptr = new char[size];
        strcpy(new_ptr, ptr);
        delete[] ptr;
        ptr = new_ptr;
    }
    void show()
    {
        cout <<"len="<<len<<"    size="<<size<<"   ptr="<<ptr<<endl;
    }
};

int main()
{
    My_string s1;
    My_string s2("lili");
    My_string s3("lililyq");
    My_string s4(s2);
    My_string s5(s2);
    s2.push_back('y');
    s2.show();
    s2.dele_back();
    s2.show();
    cout<<"第一个字符："<<s2.at(2)<<endl;
    cout<<s2.my_ptr()<<endl;
    cout<<s2.my_len()<<endl;
    cout<<s2.my_size()<<endl;
    //while(1)
   // {
    //    s2.doubledilatation();
    //}
    return 0;
}