c++运算符重载总结

今天学了运算符的重载，对于c++，相比C语言而言语法又多且杂，难背又难记，最近真有点懈怠......还是要加油

#ifndef _STRING_H_
#define _STRING_H_
#include <iostream>

using namespace std;

class String
{
public:
    //static int MAX_LEN;
    //friend class StringTool;
    //friend void print(const String &s1);
    String();
    String(char *str);
    ~String();
    String(const String& other);
    void myStrcat();
    void Display() const;
    void setMAXLEN(int maxLen);
    int getMAXLEN();
    String& operator=(const String& other);
    String& operator=(char *str);
    char& operator[](unsigned int index);
    const char& operator[](unsigned int index) const;
    String& operator+=(const String &s);    
    friend String operator+(const String& s1, const String& s2);
    friend ostream& operator<<(ostream &out, const String &s);
    friend istream& operator>>(istream &in,String& s);
    operator char *();
private:
    char *str_;
    static const int MAX_LEN = 1024;
    //String(const String& other);//绂佹鎷疯礉
};


#endif

#include <iostream>
#include <string.h>
#include "String.h"

using namespace std;

//int String::MAX_LEN = 1024;

String::String()
{
    str_ = new char('\0');
    cout <<  "default constrcutor String" << endl;
}

String::String(char *str)
{
    cout << "construct String" << endl;//str_ = str;
    int len = strlen(str) + 1;
    str_ = new char[len];
    memset(str_,0,len);
    strcpy(str_,str);
}

String::String(const String& other)
{
    int len = strlen(other.str_) + 1;
    str_ =  new char[len];
    memset(str_,0,len);
    strcpy(str_,other.str_);
}

String::~String()
{
    cout << "destroy String" << endl;  
    delete [] str_;
}

String::operator char*()
{
    return str_;
}

String& String::operator=(const String& other)
{
    if(this == &other)
    {
        return *this;
    }

    int len = strlen(other.str_) + 1;    
    delete [] str_;
    str_ = new char[len];
    memset(str_,0,len);
    strcpy(str_,other.str_);

    return *this;
}

String& String::operator=(char *str)
{
    cout << "operator char *str" << endl;
    
    int len = strlen(str) + 1;    
    delete [] str_;
    str_ = new char[len];
    memset(str_,0,len);
    strcpy(str_,str);

    return *this;
}

char& String::operator[](unsigned int index)
{
    cout << "no const []" << endl;
    return const_cast<char&>(static_cast<const String&>(*this)[index]);
}

const char& String::operator[](unsigned int index) const
{
    cout << "const []" << endl;
    
    return str_[index];
}

String operator+(const String& s1, const String& s2)
{
    /*
    int len = strlen(s1.str_) + strlen(s2.str_) + 1;
    char *newptr= new char[len];
    memset(newptr,0,len);
    strcpy(newptr,s1.str_);
    strcat(newptr,s2.str_);
    String temp(newptr);
    */
    
    String temp(s1);

    temp += s2;

    return temp;
}

String& String::operator+=(const String &s)
{
    int len = strlen(str_) + strlen(s.str_) + 1;
   
    char *newptr = new char[len];
    strcpy(newptr,str_);
    strcat(newptr,s.str_);
    delete [] str_;
    str_ = new char[len];
    strcpy(str_,newptr);
    return *this;
}

ostream& operator<<(ostream &out, const String& s)
{
    out << s.str_;
    return out;
}

istream& operator>>(istream &in, String& s)
{
    char buffer[1024];
    in >> buffer;
    int len = strlen(buffer) + 1;
    delete [] s.str_;
    s.str_ = new char[len];
    strcpy(s.str_,buffer);
    return in;
}

void String::Display() const
{
    cout << str_ << endl;
}

void String::setMAXLEN(int maxLen)
{
}

int String::getMAXLEN()
{
    return MAX_LEN;
}

#include <iostream>
#include "String.h"
#include "Stringtool.h"

using namespace std;

int main()
{
   #if 0
    String s1;

    s1 = "hello";
    
    cout << s1[1] << endl;
    
    s1[1] = 'E';
    
    s1.Display();

    String s2("world");
    cout << s2[1] << endl;
    //s[2] = 'L';

    String s3("kkk");

    //s3 = s1 + s2;
    s3+=s1;//s3 = s3 + s1;

    s3.Display();
    #endif
    
    String s("hello world");

    cout << s << endl;
    
    cin >> s;

    cout << s << endl;
    
    char *ptr = static_cast<char *>(s);
     
    cout << ptr << endl;

    return 0;
}