c++ - C++前向声明错误

Question

我有一个像这样的错误

    In file included from Level.hpp:12,
                 from main.cpp:4:
Corridor.hpp: In method `void Game::Corridor::update()':
Corridor.hpp:41: invalid use of undefined type `class Game::Level'
Corridor.hpp:13: forward declaration of `class Game::Level'
Corridor.hpp:42: invalid use of undefined type `class Game::Level'
Corridor.hpp:13: forward declaration of `class Game::Level'
Corridor.hpp:43: invalid use of undefined type `class Game::Level'
Corridor.hpp:13: forward declaration of `class Game::Level'
Corridor.hpp:44: invalid use of undefined type `class Game::Level'
Corridor.hpp:13: forward declaration of `class Game::Level'

走廊和水平是...

  // Corridor.hpp

#ifndef GAME_CORRIDOR_HPP
#define GAME_CORRIDOR_HPP

#include <Moot/Math.hpp>

//#include <Level.hpp>
#include <GameWindow.hpp>

namespace Game
{
    class Level; // <-- LINE 13

    class Corridor
    {
        static const unsigned int defaultLevelDepth = 800;

        Moot::Math::Vector3D wp1, wp2, wp3, wp4;
        Moot::Math::Vector2D sp1, sp2, sp3, sp4;

        Level * p_level;

    public:

        Corridor(Moot::Math::Vector3D setFirstPoint, Moot::Math::Vector3D setSecondPoint) 
        {
            wp1 = setFirstPoint;
            wp2 = setSecondPoint;

            wp3 = setFirstPoint;
            wp3.z += defaultLevelDepth;

            wp4 = setSecondPoint;
            wp4.z += defaultLevelDepth;
        }


        void update() {

            sp1 = p_level->getLevelCamera().convert3DVectorWithScreenAlgorithm(wp1); // <- LINE 41 etc.
            sp2 = p_level->getLevelCamera().convert3DVectorWithScreenAlgorithm(wp2);
            sp3 = p_level->getLevelCamera().convert3DVectorWithScreenAlgorithm(wp3);
            sp4 = p_level->getLevelCamera().convert3DVectorWithScreenAlgorithm(wp4);


            //p_level->getLevelCamera();
        }

        void draw()//const
        {
            Moot::Color tempColor;

            windowInstance().graphics().drawQuad( sp1.x, sp1.y, tempColor,
                                                                                sp2.x,sp2.y, tempColor,
                                                                                sp3.x, sp3.y, tempColor,
                                                                                sp4.x,sp4.y, tempColor, 1);
        }


        void setLevel(Level* setLevel) {
            p_level = setLevel;
        }

    };
}

#endif

和

// Level.hpp

#ifndef GAME_LEVEL_HPP
#define GAME_LEVEL_HPP

#include <Moot/Forward.hpp>
#include <Moot/Window.hpp>
#include <Moot/Math.hpp>

#include <GameWindow.hpp>
#include <Camera.hpp>
#include <Corridor.hpp>
#include <Player.hpp>

#include <vector>


namespace Game
{
    class Level
    {

        typedef Corridor* p_corridor;
        typedef std::vector<p_corridor> CorridorList;
        typedef CorridorList::reverse_iterator ReverseCorridorItter;

        CorridorList m_map;
        Camera       m_camera;
        Player         m_player;


    public:

        Level()
        {
            m_player.setLevel(this);

            // Lots of vertices being defined into m_map.


            // Loop through and set camera
            ReverseCorridorItter rit;

            for(rit = m_map.rbegin(); rit != m_map.rend(); rit++)
                (*rit)->setLevel(this);


        }


        ~Level()
        {
            ReverseCorridorItter rit;

            for(rit = m_map.rbegin(); rit != m_map.rend(); rit++) 
                delete (*rit);

            m_map.clear();
        }


        void update() 
        {
            // Temp delete when input and player are implimented.
            if(pad[0].buttons & PAD_UP)
                m_camera.updateTargetOffsets(0, -2);

            if(pad[0].buttons & PAD_DOWN)
                m_camera.updateTargetOffsets(0, 2);

            if(pad[0].buttons & PAD_LEFT)
                m_camera.updateTargetOffsets(-2, 0);

            if(pad[0].buttons & PAD_RIGHT)
                m_camera.updateTargetOffsets(2, 0);

            m_player.update();


            ReverseCorridorItter rit;

            for (rit = m_map.rbegin(); rit != m_map.rend(); rit++)
                (*rit)->update();
        }


        void draw() // const // EH!!! wtf ReverseIter isn't a member
        {
            m_player.draw();


            ReverseCorridorItter rit;

            for (rit = m_map.rbegin(); rit != m_map.rend(); rit++)
                (*rit)->draw();

        }


        Camera& getLevelCamera() {
            return m_camera;
        }

    };
}

#endif

据我所知，指针正在设置，但是当我尝试从 Level 访问函数时，BOOM！

谢谢。

PS：如果有区别的话，编译器是 gcc 2.95.2。

编辑

更新了完整的代码。

score 11 · Accepted Answer

你是#include-ingLevel的完整声明：

#include <Level.hpp>

...然后您尝试转发声明Level：

namespace Game
{
    class Level;

不要这样做。选择一个或另一个。（编辑）或者至少将前向声明放在#include完整声明的 -ion 之前。如果您所做的game_corridor.hpp只是设置指向 a 的指针Level，那么前向声明应该没问题。但是，如果您需要Level从 HPP 文件中调用函数，则需要#include完整的声明。

编辑2：

根据您对 OP 的澄清编辑，您必须 #include完整声明Level，而不是尝试使用前向声明。

score 2 · Accepted Answer

如果您前向声明Game::Level，则不要#include 它。在不太相关的注释中，使用#include "header.hpp"， not #include <header.hpp>。

根据您的更新进行编辑Game::Corridor::update()：将标头外部的定义放入实现文件中。Game::Level这样，除了它存在并且它是一种类型之外，编译不需要知道任何事情。

score 0 · Accepted Answer

问题是 Corridor 不知道 Level 是什么，因为它不能真正#include Level.hpp，因为 Level.hpp 就是 #included Corridor.hpp。

潜在的问题是您正在尝试#include 源文件。真正潜在的问题是，#include当您没有将代码分成源文件和头文件时，您正在使用。以下是如何拆分它。（我假设您熟悉将源文件编译为目标文件，然后将它们链接到可执行文件中。）

走廊.hpp：

#ifndef GAME_CORRIDOR_HPP
#define GAME_CORRIDOR_HPP

#include <Moot/Math.hpp>

#include <Level.hpp>

namespace Game
{
  class Level;

  class Corridor
  {
    static const unsigned int defaultLevelDepth = 800;

    Moot::Math::Vector3D wp1, wp2, wp3, wp4;
    Moot::Math::Vector2D sp1, sp2, sp3, sp4;

    Level * p_level;

  public:

    Corridor(Moot::Math::Vector3D setFirstPoint, Moot::Math::Vector3D setSecondPoint);

    void update();
    void draw();

    void setLevel(Level* setLevel);
  };
}

#endif

走廊.cpp：

#include "Corridor.hpp"

namespace Game
{
  Corridor::Corridor(Moot::Math::Vector3D setFirstPoint, Moot::Math::Vector3D setSecondPoint) 
  {
    wp1 = setFirstPoint;
    wp2 = setSecondPoint;
    wp3 = setFirstPoint;
    wp3.z += defaultLevelDepth;
    wp4 = setSecondPoint;
    wp4.z += defaultLevelDepth;
  }

  void Corridor::update() 
  {  
    sp1 = p_level->getLevelCamera().convert3DVectorWithScreenAlgorithm(wp1);
    sp2 = p_level->getLevelCamera().convert3DVectorWithScreenAlgorithm(wp2);
    sp3 = p_level->getLevelCamera().convert3DVectorWithScreenAlgorithm(wp3);
    sp4 = p_level->getLevelCamera().convert3DVectorWithScreenAlgorithm(wp4);
  }

  // and so on

}

c++ - C++前向声明错误

3 回答 3

编辑2：

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