C ++-没有适当的默认构造函数 [英] C++ - No appropriate default constructor available

问题描述

我在使用一个非常简单的程序时遇到了麻烦。它将引发错误：

I'm having trouble with a very simple program. It throws the errors:

错误C2512：播放器：没有合适的默认构造函数

IntelliSense： Player类不存在默认构造函数

I感觉这与在Game.h中将Player类声明为私有变量有关，但是我不明白为什么。任何帮助将不胜感激。

I have a feeling it's got something to do with declaring the Player class as a private variable in the Game.h but I can't see why. Any help would be much appreciated.

Game.h

#pragma once
#include "Player.h"

class Game
{
public:
    Game(void);
    void start(void);
    ~Game(void);
private:
    Player player;
};

Game.cpp

#include "Game.h"

Game::Game(void)
{
    Player p(100);

    player = p;
}

void Game::start()
{
    ...
}

Game::~Game(void)
{
}

Player.h

#pragma once
class Player
{
public:
    Player(int);
    ~Player(void);

private:
    int wallet;
};

Player.cpp

Player.cpp

#include "Player.h"
#include <iostream>

using namespace std;

Player::Player(int walletAmount)
{
    wallet = walletAmount;
}

Player::~Player(void)
{
}

推荐答案

与C＃相反，此声明;

In contrast to C#, this declaration;

Player player;

...是 Player ，这意味着到您在构造函数中分配它时，它已经构造为没有参数。

...is an instantiation of the type Player, which means that by the time you're assigning it inside the constructor, it has already been constructed without a parameter.

您需要做的是告诉该类如何初始化 player 在您附加到构造函数标头的初始化列表中；

What you need to do is to tell the class how to initialize player in what is called an initializer list that you append to the constructor header;

Game::Game(void) : player(100)
{
...

...告诉编译器首先使用该构造函数初始化 player 首先使用默认的无参数构造函数，然后然后为其赋值。

...which tells the compiler to use that constructor to initialise player in the first place instead of first using the default no-parameter constructor and then assigning to it.

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