c++String类的运算符重载---21

原创博文，转载请标明出处--周学伟http://www.cnblogs.com/zxouxuewei/

 一，创建测试程序包

测试代码如下：

/* Date: 2017-5-4
 * Description: String operator overload test program
 * Filename: string_operator.h
 * Author: Myron Zhou
 */

#ifndef __STRING_OPERATOR_h_
#define __STRING_OPERATOR_h_  

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

using namespace std;  

class MyString
{
public:
    //三个重载的构造函数
    MyString();
    MyString(const char* str);
    MyString(const MyString& str);
    //析构函数
    ~MyString();  

    //重载运算符
    MyString& operator = (const MyString& str);
    char&  operator[](int index);                                                   //访问下标
    friend ostream& operator << (ostream& out, const MyString& str);                //重载输出操作符
    friend istream& operator >> (istream& in, MyString& str);                       //重载输入操作符
    friend MyString operator + (const MyString& str1, const MyString& str2);        //重载加号操作符，注意返回引用不行
    friend MyString operator += (MyString& str1, const MyString& str2);             //重载+=操作符
    friend bool operator == (const MyString& str1, const MyString& str2);           //重载相等操作符
    friend bool operator != (const MyString& str1, const MyString& str2);           //重载不相等操作符    

private:
    char* p;
    int len;
};

#endif  

/* Date: 2017-5-4
 * Description: String operator overload test program
 * Filename: string_operator.cpp
 * Author: Myron Zhou
 */
#include "string_operator.h"
using namespace std; 

//默认构造函数，初始化为空串
MyString::MyString()
{
    len = ;
    p = new char[len + ];
    p[] = '\0';
}
//构造函数，用一个字符串初始化
MyString::MyString(const char* str)
{
    len = strlen(str);
    p = new char[strlen(str) + ];
    strncpy(p, str,len+);
}
//拷贝构造函数，用另外一个string初始化
MyString::MyString(const MyString& str)
{
    len = str.len;
    p = new char[strlen(str.p) + ];
    strncpy(p,  str.p, strlen(str.p) + );
}
//析构函数
MyString::~MyString()
{
    delete[] p;
}
//重载赋值操作符( = )
MyString& MyString::operator = (const MyString& str)
{
    if (this->p == str.p)
    {
        return *this;
    }
    delete[] p;
    len = str.len;
    p = new char[len + ];
    strncpy(p,  str.p, len + );
    return *this;
}
//重载输出操作符( << )
ostream& operator << (ostream& out, const MyString& str)
{
    out << str.p;
    return out;
}
//重载输入操作符( >> )
istream& operator >> (istream& in, MyString& str)
{
    in >> str.p;
    return in;  

}
//重载加号操作符( + )
MyString operator + (const MyString& str1, const MyString& str2)
{
    MyString str;
    delete[] str.p;
    str.len = str1.len + str2.len;
    str.p = new char[str.len + ];
    strncpy(str.p,  str1.p, str.len + );
    strncat(str.p,  str2.p, str.len + );
    return str;
}
//重载相加赋值操作符( += )
MyString operator += (MyString& str1, const MyString& str2)
{
    str1 = str1 + str2;
    return str1;
}
//重载相等操作符
bool operator == (const MyString& str1, const MyString& str2)
{
    if (strcmp(str1.p, str2.p) == )
    {
        return true;
    }
    return false;
}
//重载不相等操作符
bool operator != (const MyString& str1, const MyString& str2)
{
    if (strcmp(str1.p, str2.p) == )
    {
        return false;
    }
    return true;
}  

//重载下标（[]）
char&  MyString::operator[](int index)
{
    return p[index];
} 

/* Date: 2017-5-4
 * Description: String operator overload test program
 * Filename: main.cpp
 * Author: Myron Zhou
 */

#include "string_operator.h"  

int main()
{
    MyString mystr("this is test program!");            //测试构造函数，用一个字符串初始化
    cout << mystr[] << endl;
    mystr[] = 'd';
    cout << mystr <<endl;
    MyString mystr2(mystr);                 //用另外一个string初始化
    cout << mystr2 << endl;
    MyString mystr3;
    mystr3 = mystr + mystr2;                //测试加号运算符，测试赋值运算符
    cout << mystr + mystr2 << endl;
    mystr3 += mystr;                        //测试+=运算符
    cout << mystr3 << endl;
    cout << (mystr == mystr2) << endl;      //测试 ==
    cout << (mystr != mystr3) << endl;      //测试 ！=
    MyString mystr4;
    cout << "good luck!" << endl;
    cin >> mystr4;                          //测试重载的输入符号( >> )
    cout << mystr4 << endl;  

    return ;
}  

二，编译运行代码