纯虚函数没有覆盖

Question

有人能帮帮我吗？

我现在遇到这个问题，无法解决

object of abstract class type is not allowed: pure virtual function has no overrider'

我在下面突出显示：

class State 
{ 
public:
    virtual void Update() = 0;
    virtual void Render();
    virtual void Enter() = 0;
    virtual void Exit() = 0;
    virtual void Resume() = 0;
protected:
    State() {} 
};

class GameState : public State
{
private:
    Level level;
    Level levels[5] = { Level(3), Level(1), Level(1), Level(2), Level(1) };
    const char* levelNames[5] = { "Level1.txt", "Level2.txt", "Level3.txt", "Level4.txt", "Level5.txt" };
    SDL_Texture* tileText;
    SDL_Texture* playerText;
    Player player;
    SDL_Surface* tileSurf;
    SDL_Surface* playerSurf;

    int m_iTickCtr = 0;
    int m_iTickMax = 1; // for animation

public:
    GameState() {}
    void Update(Level& l, Player& p, int& c) ; // Level& level, Player& player, int& c
    void Render(Level& l, Player& p);
    void Enter();
    void Exit();
    void Resume() { cout << "Resuming Game..." << endl; }
    enum sfx { jump, boom, laser };
};

class TitleState : public State
{
public:
    TitleState() {}
    virtual void Update();
    void Render();
    void Enter(); 
    void Exit();
    void Resume() {}
    enum btn { play, exit };
private: 
    vector<Button*> m_vButtons;
};

void TitleState::Update()
{
    /*
    if (Game::Instance()->KeyDown(SDL_SCANCODE_B) == 1)
        Game::Instance()->GetAM()->PlaySound(sfx::boop);
    */
    for (int i = 0; i < (int)m_vButtons.size(); i++)
        m_vButtons[i]->Update();
    // Parse buttons.
    if (m_vButtons[btn::play]->Clicked())
        Game::Instance()->GetFSM()->ChangeState(new GameState()); // here 'GameState' has problems.
    else if (m_vButtons[btn::exit]->Clicked())
        Game::Instance()->DoQuit();
}

Answer 1

在你的子class、GameState中，你必须为void Update()创建一个覆盖函数，它在抽象class、State.

也许您认为您这样做了，因为您创建了 void Update(Level& l, Player& p, int& c)，但由于此函数的签名与 void Update() 不同，因此它不会覆盖它。

纯虚函数没有覆盖

pure virtual function has no overrider

c++

virtual