C++之实现MyString类

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1.MyString.h

#pragma once#include<iostream>using namespace std;class MyString{public:    MyString(const char *str = NULL);    MyString(const MyString&another);    MyString&operator=(const MyString&another);    char* c_str();    MyString operator+(const MyString&another);    bool operator>(const MyString&another);    bool operator<(const MyString&another);    bool operator==(const MyString&another);    char &operator[](int idx);    char at(int idx);    friend istream& operator>>(istream& in,MyString & str);    friend ostream& operator<<(ostream& out,const MyString & str);    ~MyString(void);private:    char *_str;};

2.MyString.cpp

#include "MyString.h"//构造函数MyString::MyString(const char *str){    if(str == NULL)    {        _str = new char[1];        _str[0] = '\0';    }    else    {        int len = strlen(str);        _str = new char[len+1];        strcpy(_str,str);    }}//拷贝构造函数MyString::MyString (const MyString&another){    int len = strlen(another._str);    this->_str = new char[len+1];    strcpy(this->_str,another._str);}//运算符=重载MyString&MyString::operator=(const MyString&another){    if(this == &another)    {        return *this;    }    else{        delete []this->_str;        int len = strlen(another._str);        this->_str = new char[len+1];        strcpy(this->_str,another._str);        return *this;    }}//获取字符char* MyString::c_str(){    return this->_str;}//运算符+重载MyString MyString::operator + (const MyString& another){    MyString mystr;    int len = strlen(this->_str)+strlen(another._str);    delete mystr._str;    mystr._str = new char[len+1];    memset(mystr._str,0,len+1);    strcat(mystr._str,this->_str);    strcat(mystr._str,another._str);    return mystr;}//运算符>重载bool  MyString::operator>(const MyString& another){    if(strcmp(this->_str,another._str)>0)        return true;    else return false;}//运算符<重载bool  MyString::operator<(const MyString& another){    if(strcmp(this->_str,another._str)<0)        return true;    else return false;}//运算符==重载bool  MyString::operator==(const MyString& another){    if(strcmp(this->_str,another._str)==0)        return true;    else return false;}//下标取值char & MyString::operator[](int idx){    return this->_str[idx];}//函数取值char  MyString::at(int idx){    return this->_str[idx];}//输入运算符重载istream& operator>>(istream& in,MyString & str){    delete []str._str;    char buf[1024];    scanf("%s",buf);    int len = strlen(buf);    str._str = new char[len+1];    strcpy(str._str,buf);    return in;}//输出运算符重载ostream& operator<<(ostream& out,const MyString & str){    out<<str._str;    return out;}//析构函数MyString::~MyString(void){    delete []this->_str;}

3.main.cpp

#include<iostream>#include "MyString.h"using namespace std;int main(){    MyString s1;    cin>>s1;    cout<<s1<<endl;    cout<<s1.c_str()<<endl;    MyString s2("hello");    cout<<"s2="<<s2.c_str()<<endl;    MyString s3(s2);    cout<<s3.c_str()<<endl;    MyString s4 = " world";    cout<<"s4="<<s4.c_str()<<endl;    MyString s5 = s3 + s4;    cout<<s5.c_str()<<endl;    if(s2<s4)       cout<<"s2<s4"<<endl;    else if(s2>s4)        cout<<"s2>s4"<<endl;    else        cout<<"s2==s4"<<endl;    system("pause");}

其实MyString类是模范C++的string类写的，string类里面有很多的成员函数，而我只实现了其中的一小部分常见的功能函数，如果有兴趣可以自己试着扩展更多的功能。

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