仿照string类，自己手动实现 My_string

代码如下

MyString.h

#ifndef MYSTRING_H
#define MYSTRING_H
#include <iostream>
#include <cstring>using namespace std;class My_string
{
private:char *ptr;         //指向字符数组的指针int size;           //字符串的最大容量int len;            //字符串当前容量public://无参构造My_string();//有参构造My_string(const char* src);My_string(int num, char value);//拷贝构造My_string(const My_string &other);//拷贝赋值My_string & operator= (const My_string &other);//析构函数~My_string();//判空bool Isvoid();//显示void show();//尾插void push_back(char value);//尾删void pop_back();//at函数实现char &at(int index);//清空函数void clear();//返回C风格字符串char *data();//返回实际长度int get_length();//返回当前最大容量int get_size();//君子函数:二倍扩容bool Add();};
#endif // MYSTRING_H

MyString.cpp

#include "MyString.h"My_string::My_string():size(15)
{this->ptr = new char[size];this->ptr[0] = '\0';            //表示串为空串this->len = 0;cout<<"无参构造"<<endl;
}//有参构造
My_string::My_string(const char* src):size(15) {this->ptr = new char[size];strcpy(ptr, src); // 复制字符串this->len = strlen(src);cout << "一个形参的有参构造" << endl;
}
My_string::My_string(int num, char value):size(15),len(num){if(num>15){cout<<"超出默认长度"<<endl;return;}this->ptr = new char[15];for(int i=0;i<num;i++){this->ptr[i] = value;}cout<<"部分形参的有参构造"<<endl;
}
//拷贝构造
My_string::My_string(const My_string &other):size(other.size),len(other.len){this->ptr = new char[size];strcpy(this->ptr, other.ptr); // 复制字符串cout<<"拷贝构造"<<endl;
}
//拷贝赋值
My_string& My_string::operator= (const My_string &other){if(this != &other){this->len =other.len;this->size = other.size;for(int i=0;i<other.len;i++){this->ptr[i] =other.ptr[i];}}cout<<"拷贝赋值"<<endl;return *this;
}
//析构函数
My_string::~My_string(){cout<<this->ptr<<"析构函数"<<endl;delete[] ptr;
}
//判空
bool My_string::Isvoid(){return this->len ==0 ? true:false;
}
//显示
void My_string::show(){for(int i=0;i<this->len;i++){cout<<*(this->ptr+i);}cout<<endl;
}
//尾插
void My_string::push_back(char value){if(this->len < this->size-1){*(this->ptr+len++) = value;}else if(this->Add()){*(this->ptr+len++) = value;}
}
//尾删
void My_string::pop_back(){this->len--;
}
//at函数实现
char& My_string::at(int index){if(index<=this->len-1){return this->ptr[index];}else {cout<<"下标越界"<<endl;exit(EXIT_SUCCESS);}
}
//清空函数
void My_string::clear(){free(this->ptr);this->ptr[0] = '\0';this->len = 0;
}
//返回C风格字符串
char* My_string::data(){return this->ptr;
}
//返回实际长度
int My_string::get_length(){return this->len;
}
//返回当前最大容量
int My_string::get_size(){return this->size;
}bool My_string::Add(){if(this->len == this->size-1){char *p = new char[size*2];strcpy(p,this->ptr);free(this->ptr);this->ptr = p;return true;}else return false;
}

main.cpp

#include "MyString.h"int main(){My_string s;cout<<"s：";s.show();My_string s1("hello");cout<<"s1：";s1.show();My_string s2(5,'A');cout<<"s2：";s2.show();My_string s3 = s2;cout<<"s3：";s3.show();s3 = s1;cout<<"s3：";s3.show();if(s3.Isvoid()){cout<<"s3空"<<endl;}else cout<<"s3非空"<<endl;cout<<"尾插：";s3.push_back('a');s3.show();cout<<"尾删：";s3.pop_back();s3.show();cout<<"查看下标4的值："<<s3.at(4)<<endl;cout<<"清空s3函数"<<endl;s3.clear();cout<<"s3：";s3.show();cout<<"s1的C风格字符串："<<s1.data()<<endl;cout<<"s1的实际长度："<<s1.get_length()<<endl;cout<<"s1当前最大容量："<<s1.get_size()<<endl;
//    cout<<"s3的二倍扩容"<<endl;
//    char c =' ';
//    while(c!='#'){
//        cin>>c;
//        s3.push_back(c);
//    }//s3.show();
}

运行结果

思维导图