C++ 重载运算符<对于结构:错误太多参数 [英] C++ Overloading operator&lt; for struct: Error too many parameters

问题描述

对于一项作业，学生必须制作一个 Card 结构来保存卡片的套装、等级和位图.这个结构需要一个重载的<"运算符比较lhs卡的Rank是否小于rhs卡并返回bool.到目前为止，这是我的 Card.h 文件:

For an assignment students have to make a Card struct that keeps the Suit, Rank and Bitmap of a Card. This struct needs an overloaded "<" operator to compare whether the lhs Card's Rank is smaller than the rhs Card and return the bool. So far this is my Card.h file:

#pragma once

#include "GameEngine.h"

struct Card
{

public:
//Constructor and Destructor
Card();
virtual ~Card();

//Methods
bool operator< (const Card& lhs, const Card& rhs)
{
    return (lhs.m_Rank < rhs.m_Rank);
}

//Enumerations
enum class Suit
{
    Diamonds,
    Clubs,
    Hearts,
    Spades,
};

enum class Rank
{
    RankAce,
    RankTwo,
    RankThree,
    RankFour,
    RankFive,
    RankSix,
    RankSeven,
    RankEight,
    RankNine,
    RankTen,
    RankJack,
    RankQueen,
    RankKing,
};

private:
//Datamembers
Bitmap *m_BmpPtr;
Rank m_Rank;
Suit m_Suit;
};

但是操作符<过载声称它有太多的参数.这不是确保可以在一次重载中比较 lhs 和 rhs 的正确方法吗?不是说我要分开吧?

However the operator< overload claims that it has too many parameters. Isn't this the right way to make sure both lhs and rhs can be compared in one overload? It's not like I have to split it up right?

非常感谢.

推荐答案

编译器认为这是一个成员函数，但成员函数operators不能有多个参数.第一个参数是隐式的 *this 而第二个是你提供的.

The compiler think this is a member function, but member function operators cannot have more than one argument. The first argument is implicitly *this while the second is the one you supply.

您可以通过剥离第一个参数并使用 *this 代替 lhs 来使其成为成员函数.否则，您可以使用惯用的解决方案并使其成为朋友:

You can make this a member function by stripping the first argument and using *this in place of lhs. Otherwise, you can use an idiomatic solution and make it a friend:

friend bool operator< (const Card& lhs, const Card& rhs)
{
    return lhs.m_Rank < rhs.m_Rank;
}

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