c++ - 类 x(继承)C++ 不存在默认构造函数

Question

我有以下三个标题:

IBaseStates.h

class IBaseStates
{
public:
    enum STATE;

    virtual void Update( STATE state ) = 0;
};

PlayerStates.h

#pragma once

#include "IBaseStates.h"
#include "Player.h"

class PlayerStates : public IBaseStates, public Player
{
public:
    enum STATE {
        FLYING,
        FALLING
    };

    int textureAmount;

    PlayerStates();
    ~PlayerStates( );

    void Update( STATE state );
};

Player.h

#pragma once

#include "StructVertex.h"
#include "SquareVertices.h"
#include "WICTextureLoader.h"

using namespace Microsoft::WRL;
using namespace DirectX;
//using namespace DirectX;

class Player : public SquareVertices
{
public:
    Player( ComPtr<ID3D11Device1> d3dDevice );
    ~Player();

    void Initialize();
    void Update();

    float x;
    float y;
    float z;
    float rotation;
    float velocity;

    ComPtr<ID3D11Buffer> vertexbuffer;
    ComPtr<ID3D11Buffer> indexbuffer;
    ComPtr<ID3D11ShaderResourceView> texture[3];
protected:
    const ComPtr<ID3D11Device1> d3dDevice;
};

为什么当我在我的 PlayerStates.cpp 文件中为我的 PlayerStates 类定义一个构造函数时，我会得到

no default constructor exists for class Player

PlayerStates.cpp

#include "pch.h"
#include "PlayerStates.h"

PlayerStates::PlayerStates()
: 
    textureAmount( 3 )
{
}

Answer 1

当您为类声明非默认构造函数时，编译器不再生成默认构造函数。所以你必须提供你自己的。

PlayerStates 需要在其自己的默认构造函数中调用其基类 Player 的默认构造函数。因此，您要么需要为 Player 提供默认构造函数，要么从 PlayerStates 的默认构造函数初始化列表中调用它的非默认构造函数。

这会隐式调用 Player::Player()。

PlayerStates::PlayerStates() : textureAmount( 3 ) {}

这会调用单参数构造函数:

PlayerStates::PlayerStates() : Player(someComPtr), textureAmount( 3 ) {}