覆盖抽象类的属性

Question

我正在定义一个类GameState和一个MainMenuGameState类.前者是一个抽象类,后者是继承它.但不知何故,我无法覆盖其属性.

GameState.h

#ifndef _GAME_STATE_H_
    #define _GAME_STATE_H_

#include <SDL2/SDL.h>

class GameState {
    public:
        virtual void loop(Uint32 deltaTime) = 0;
        virtual void render() = 0;
        virtual void event(SDL_Event * event) = 0;

        bool stopRenderPropagation = false;
        bool stopLoopPropagation = false;
};

#endif

MainMenuGameState.h

#ifndef _MAIN_MENU_GAME_STATE_H_
    #define _MAIN_MENU_GAME_STATE_H_

#include "../Game.h"

class MainMenuGameState : public GameState {
    public:
        MainMenuGameState(Game * pGame);

        void loop(Uint32 deltaTime);
        void render();
        void event(SDL_Event * event);

        bool stopRenderPropagation = true;
        bool stopLoopPropagation = true;

    private:
        Game * game;

        int xOffset = 0;
        int yOffset = 0;
};

#endif

因此,在对MainMenuGameState对象进行实例化之后,我期望stopRenderPropagation并stopLoopPropagation成为true,但它们是false.

由于某种原因,我也没有运气在构造函数中覆盖它们.

MainMenuGameState::MainMenuGameState(Game * pGame) {
    game = pGame;

    xOffset = rand() % 20;
    yOffset = rand() % 20;

    stopRenderPropagation = true;
    stopLoopPropagation = true;
}

在那之后,他们仍然是真的.我不知道天气这是我的构造函数的问题,还是我误解了c ++中的多态性.

MainMenuGameState的实例存储在一个vector<GameState *>,这可能是问题吗？我正在访问这样的属性:

if(gameStates.begin() != gameStates.end()) {
    std::vector<GameState *>::iterator it = gameStates.end();
    do {
        --it;
    } while(it != gameStates.begin() && (*it)->stopLoopPropagation == false);

    while(it != gameStates.end()) {
        (*it)->loop(deltaTime);
        ++it;
    }
}

谢谢您的帮助!

Answer 1

您的派生类声明了另一对成员在基类中具有相同名称的成员,因此"隐藏"了基类.

你应该接受构造函数中那些成员的初始值,或者如果它们是永远不会改变的类的固定属性,你应该使它们成为成员函数,就像在

class GameState {
    public:
        ...    
        virtual bool stopRenderPropagation() { return false; }
        virtual bool stopLoopPropagation() { return false; }
};

class MainMenuGameState : public GameState {
    public:
        ...    
        bool stopRenderPropagation() { return true; }
        bool stopLoopPropagation() { return true; }
        ...
};