[c++]String字串類的運算子多載

標籤：c++   重載string   

在c++中有一個新定義的類型string，可以不用那麼麻煩的操作字串，並且一些進階的運算子多載讓她的使用更加便捷

下面是String類的定義和成員函數的定義：

#ifndef operator_operator_h#define operator_operator_h#include<iostream>#include<string.h>using namespace std;class String{    friend ostream& operator<<(ostream &out, const String &s);    friend istream& operator>>(istream &in, String &s);public:    String(const char *str = NULL)    {        if(str == NULL)        {            m_data = new char[1];            m_data[0] = '\0';        }        else        {            m_data = new char[strlen(str)+1];            strcpy(m_data,str);        }    }    String(const String &s)    {        m_data = new char[strlen(s.m_data)+1];        strcpy(m_data,s.m_data);    }    String& operator=(const String &s)    {        if(this != &s)        {            free(m_data);            m_data = new char[strlen(s.m_data)+1];            strcpy(m_data,s.m_data);        }        return *this;    }    ~String()    {        delete []m_data;    }    friend ostream& operator<<(ostream &out, const String &s)    {        out<<s.m_data;        return out;    }    friend istream& operator>>(istream &in, String &s)    {        in>>s.m_data;        return in;    }    String operator+(const String &s); //s = s1 + s2    String operator+=(const String &s); //s1 += s2    char&  operator[](int index);    bool operator==(String &s);    bool operator!=(String &s);    bool operator>(String &s);   //s1 > s2    bool operator<=(String &s);    bool operator<(String &s);    bool operator>=(String &s);private:    char *m_data;};String String::operator+=(const String &s) //s1 += s2{    m_data = new char[sizeof(m_data)+1];    strcat(m_data,s.m_data);    return *this;}String String::operator+(const String &s)//s = s1 + s2{    strcat(m_data, s.m_data);    return *this;}bool String::operator==(String &s){    if(strcmp(m_data, s.m_data)==0)        return true;    return false;}bool String::operator!=(String &s){    if(strcmp(m_data,s.m_data)!=0)        return true;    return false;}bool String::operator>(String &s)   //s1 > s2{    if(strcmp(m_data,s.m_data)>0)        return true;    return false;}bool String::operator<=(String &s){    if(strcmp(m_data,s.m_data)>=0)        return true;    return false;}bool String::operator<(String &s){    if(strcmp(m_data,s.m_data)<0)        return true;    return false;}bool String::operator>=(String &s){    if(strcmp(m_data,s.m_data)<=0)        return true;    return false;}char&  String::operator[](int index){//    char*p= m_data;//    return *(p+index);    return m_data[index];}#endif

再下面是測試程式：

#include "operator.h"int main(){    String s("s");    String s1("s");    String s2;    //String s3;    //s2 = s+s1;    //s+=s1;    //cout<<"s+=s1="<<s<<endl;    cout<<"s[2] = "<<s[0]<<endl;//    if(s == s1)//        cout<<1<<endl;//    if(s != s1)//        cout<<0<<endl;//    if(s > s1)//        cout<<"s>s1"<<endl;//    if(s >= s1)//        cout<<"s>=s1"<<endl;//    if(s < s1)//        cout<<"s<s1"<<endl;//    if(s <=s1)//        cout<<"s<=s1"<<endl;    //cin>>s3;    //cout<<"s3="<<s3<<endl;//請分開測試    return 0;}

輸入S3以後不知道為什麼就成了大寫

[c++]String字串類的運算子多載