关于#c++#的问题：关于多种运算符重载的问题

Question

关于多种运算符重载的问题，最好多几条注释，解释清楚一点，注意其返回值的不同

Answer 1

代码：

#include <iostream>
using namespace std;
class CStr
{
private:
    char* data;
    int len;
public:
    CStr(const char* d = 0)
    {
        //cout << "construct----------" << endl;
        if (d == 0)
        {
            data = 0;
            len = 0;
        }
        else
        {
            len = 0;
            while (d[len] != '\0')
                len++;

            data = new char[len + 1];//多申请一个字节给\0
            for (int i = 0; i < len; i++)
                data[i] = d[i];
            data[len] = '\0'; //结束符
        }
        
        
    }
    ~CStr() 
    {
        //cout << "disconstruct....." << endl;
        //析构函数中不要delete data;否则+运算回得不到结果
    }

    CStr& operator = (CStr& s)
    {
        //cout << "=:" << endl;
        delete[] data;
        len = s.len;
        data = new char[len + 1];
        for (int i = 0; i < len; i++)
            data[i] = s.data[i];
        data[len] = '\0';
        return *this;
    }

    CStr operator +(const CStr& a)
    {
        //cout << "+" << endl;
        char* p = new char[len + a.len + 1];
        int i = 0;
        for (; i < len; i++)
            p[i] = data[i];
        for (int j = 0; j < a.len; j++)
            p[i + j] = a.data[j];
        p[len + a.len] = '\0';
        CStr t(p);
        delete[] p;
        return t;
    }

    CStr operator +=(const CStr& a)
    {
        this->data = (char*)realloc(this->data, len + a.len + 1); //扩容
        for (int j = 0; j < a.len; j++)
            this->data[len + j] = a.data[j];
        this->data[len + a.len] = '\0';
        len += a.len; //修正长度
        return *this;
    }

    bool operator >(const CStr& a)
    {
        int t = len > a.len ? a.len : len;
        for (int i = 0; i < t; i++)
        {
            if (data[i] > a.data[i])
                return true;
        }
        return false;
    }
    bool operator <(const CStr& a)
    {
        int t = len > a.len ? a.len : len;
        for (int i = 0; i < t; i++)
        {
            if (data[i] < a.data[i])
                return true;
        }
        return false;
    }
    bool operator ==(const CStr& a)
    {
        if (len != a.len)
            return false;
        
        for (int i = 0; i < len; i++)
        {
            if (data[i] != a.data[i])
                return false;
        }
        return true;
    }

    char operator [](int index)
    {
        if (index < len)
            return data[index];
        else
            return '\0';
    }

    friend ostream& operator <<(ostream& out, const CStr& a)
    {
        out << a.data;
        return out;
    }

};

int main()
{
    char buf[100] = { 0 };
    cout << "请输入一个字符串创建CStr 实例a：" << endl;
    cin >> buf;
    CStr a(buf);

    cout << "请输入一个字符串创建CStr 实例b：" << endl;
    cin >> buf;
    CStr b(buf);

    CStr c;
    c = a;
    cout << "CStr c=a; c:" << c << endl;

    CStr d = a + b;

    cout << "CStr d=a+b; d:" << d << endl;

    cout << "a>b:" << (a > b) << endl;

    cout << "请输入要获取的实例a的元素下标：";
    int index;
    cin >> index;
    cout << "a[" << index << "]=" << a[index] << endl;


    return 0;
}