23 运算符重载（二）

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++运算符重载

//Integer.h#ifndef _INTEGER_H_#define _INTEGER_H_class Integer{public:    Integer(int n);    ~Integer();    Integer& operator++();    //friend Integer& operator++(Integer& i);    Integer operator++(int n);    //friend Integer operator++(Integer& i, int n);    void Display() const;private:    int n_;};#endif // _INTEGER_H_//Integer.cpp#include "Integer.h"#include <iostream>using namespace std;Integer::Integer(int n) : n_(n){}Integer::~Integer(){}Integer& Integer::operator ++(){    //cout<<"Integer& Integer::operator ++()"<<endl;    ++n_;    return *this;}//Integer& operator++(Integer& i)//{//  //cout<<"Integer& operator++(Integer& i)"<<endl;//  ++i.n_;//  return i;//}Integer Integer::operator++(int n){    //cout<<"Integer& Integer::operator ++()"<<endl;    //n_++;    Integer tmp(n_);    n_++;//n_本身++    return tmp;//返回一个临时对象，其没有++}//Integer operator++(Integer& i, int n)//{//  Integer tmp(i.n_);//  i.n_++;//  return tmp;//}void Integer::Display() const{    cout<<n_<<endl;}//main.cpp#include "Integer.h"#include <iostream>using namespace std;int main(void){    Integer n(100);    n.Display();    Integer n2 = ++n;    n.Display();    n2.Display();    Integer n3 = n++;    n.Display();    n3.Display();    return 0;}

//String.h#ifndef _STRING_H_#define _STRING_H_class String{public:    explicit String(const char* str="");    String(const String& other);    String& operator=(const String& other);    String& operator=(const char* str);    bool operator!() const;    ~String(void);    void Display() const;private:    char* AllocAndCpy(const char* str);    char* str_;};#endif // _STRING_H_//String.cpp#pragma warning(disable:4996)#include "String.h"#include <string.h>#include <iostream>using namespace std;String::String(const char* str){    str_ = AllocAndCpy(str);}String::String(const String& other){    str_ = AllocAndCpy(other.str_);}String& String::operator=(const String& other){    if (this == &other)        return *this;    delete[] str_;    str_ = AllocAndCpy(other.str_);    return *this;}String& String::operator=(const char* str){    delete[] str_;    str_ = AllocAndCpy(str);    return *this;}bool String::operator!() const{    return strlen(str_) != 0;}String::~String(){    delete[] str_;}char* String::AllocAndCpy(const char* str){    int len = strlen(str) + 1;    char* newstr = new char[len];    memset(newstr, 0, len);    strcpy(newstr, str);    return newstr;}void String::Display() const{    cout<<str_<<endl;}//main.cpp#include "String.h"#include <iostream>using namespace std;int main(void){    String s1("abc");    String s2(s1);    String s3;    s3 = s1;//调用=运算符重载 String& operator=(const String& other);    s3.Display();    s3 = "xxxx";//调用=运算符重载 String& operator=(const char* str);    s3.Display();    return 0;}

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