类没有命名类型C++编译错误

Question

我知道这个问题在 stackoverflow 上已经被回答过很多次了，我一直在搜索它们，但仍然无法解决。这种情况下的问题可能是由于所谓的循环依赖关系造成的，我已经尝试了另一篇文章中提到的一些解决方案，例如前向声明或放入标头保护，但仍然不起作用。我不知道为什么只有 ItemComponent 文件会出现此错误，而其余文件都工作正常。

编辑：编译 InputController.hpp 文件时发生第 13 行错误：“错误：‘ItemComponent’未命名类型；您的意思是‘TileComponent’吗？”

这是文件，我使用 c++17 和 premake5:

ItemComponent.hpp

#pragma once

#include "Components.hpp"
#include <SDL2/SDL_ttf.h>
#include <SDL2/SDL.h>
#include "../Game.hpp"
#include "../TextureManager.hpp"
#include <map>

class ItemComponent : public Component
{
public:
    int box;
    int tWidth, tHeight;
    int width , height;
    int scale;

    struct ToolInfo
    {
        int x;
        int y;
        SDL_Texture* tex;
    };
    
    std::map<int, ToolInfo> ToolMap;
    std::map<std::string, int> ItemMap;
    SDL_Rect bracket[2], src, dest;
    SDL_Texture *tex;

    int text_width;
    int text_height;
    SDL_Surface *surface;
    SDL_Texture *textTex;
    SDL_Rect textRect;
    SDL_Color textColor = {27, 27, 27, 160};
    TTF_Font *font;
    std::string text = "Unequipped";
    SpriteComponent* sprite;

    ItemComponent()
    {
        // Toolbox pos 
        tWidth = 64;
        tHeight = 64;
        box = 2;
        scale = 3;

        // Tool render initialization
        width = height = 16;
        tex = TextureManager::LoadTexture("game/assets/Objects/Items/tools and meterials.png");
        ToolInfo hoe = { x: width*2, y: height*0, tex: tex};
        ToolInfo axe = { x: width*1, y: height*0, tex: tex};
        ToolMap.emplace(1, hoe);
        ToolMap.emplace(2, axe);
        ItemMap.emplace("Hoe", 1);
        ItemMap.emplace("Axe", 2);

        // Text
        font = TTF_OpenFont("game/assets/Font/UniversCondensed.ttf", 20);
    }
    ~ItemComponent() {};

    void RenderToolbox();
    void RenderText();
    void RenderUpdateToolbox(std::string item);
    void UpdateText(std::string newText);

    void init() override
    {
        // Toolbox pos
        for (int i = 0; i < box; i++)
        {
            bracket[i].x = tWidth * (i+1) + (i * 10);
            bracket[i].y = 25;
            bracket[i].w = tWidth;
            bracket[i].h = tHeight;
        }
        sprite = &entity->getComponent<SpriteComponent>();
    }

    void draw() override
    {
        RenderText();
        RenderToolbox();
        if (sprite->action.onHold)
        { RenderUpdateToolbox(sprite->action.name); }

        for (int i = 0; i < box; i++)
        {
            src.x = ToolMap[i+1].x;
            src.y = ToolMap[i+1].y;
            src.w = width;
            src.h = height;
            tex = ToolMap[i+1].tex;

        dest.x = bracket[i].x + 10;
        dest.y = bracket[i].y + 10;
        dest.w = width * scale;
        dest.h = height * scale;
        TextureManager::Draw(tex, src, dest, SDL_FLIP_NONE);
    }
}

private:
};

#endif // TOOLCOMPONENT_HPP

输入控制器.hpp

#pragma once

#include "Components.hpp"
#include <SDL2/SDL.h>
#include <iostream>
#include "../Game.hpp"
class InputController : public Component
{
public:
    TransformComponent *transform;
    SpriteComponent *sprite;
    ItemComponent *item; // Error occurred here ****

    InputController() = default;
    ~InputController() {}

    void init() override
    {
        item = &entity->getComponent<ItemComponent>();
        transform = &entity->getComponent<TransformComponent>();
        sprite = &entity->getComponent<SpriteComponent>();
    }
    // Codes....
    void update() override;
    void draw() override;
};

Compnents.hpp（包括所有标头）

#pragma once

#include "ECS.hpp"
#include "TransformComponent.hpp"
#include "SpriteComponent.hpp"
#include "ItemComponent.hpp"
#include "InputController.hpp"
#include "ColliderComponent.hpp"
#include "TileComponent.hpp"

Answer 1

您应该能够通过

解决问题

1. 避免“包含全部”，而只包含您需要的内容。
2. 尽可能长时间地使用前向声明，甚至延迟

   #include

   指令，直到在类的定义之后。这可以帮助避免出现以下情况：包含的标头需要当前标头中的类定义完整。

根据问题中的信息，以下代码应该可以工作。请注意，由于缺乏有关

Component

定义位置的信息，我为此使用

Comp.hpp

。另外，我会忽略您未定义的类型的任何成员。

ItemComponent.hpp

#pragma once

#include "Comp.hpp" // parent class required at class definition

class SpriteComponent; // full type definition not needed for the body of the class

class ItemComponent : public Component
{
public:
    ...
    SpriteComponent* sprite;

    ItemComponent()
    {
        ...
    }
    ~ItemComponent() {};

    void RenderToolbox();
    void RenderText();
    void RenderUpdateToolbox(std::string item);
    void UpdateText(std::string newText);

    void init() override;
    {

    }

    void draw() override;
}

private:
};

#include "SpriteComponent.hpp" // required for the definitions of draw and init

inline void ItemComponent::init()
{
    ...
    sprite = &entity->getComponent<SpriteComponent>();
}

inline void ItemComponent::draw()
{
    ...
    if (sprite->action.onHold)
    { RenderUpdateToolbox(sprite->action.name); }
    ...
}

InputController.hpp

#include "Comp.hpp"

// pointers in the class body don't require the following types to be complete:
class ItemComponent;
class SpriteComponent;
class TransformComponent;

class InputController : public Component
{
public:
    TransformComponent *transform;
    SpriteComponent *sprite;
    ItemComponent *item;

    InputController() = default;
    ~InputController() {}

    void init() override;
    // Codes....
    void update() override;
    void draw() override;
};


// include definitions required in init
#include "ItemComponent.hpp"
#include "TransformComponent.hpp"
#include "SpriteComponent.hpp"

inline void InputController::init()
{
    item = &entity->getComponent<ItemComponent>();
    transform = &entity->getComponent<TransformComponent>();
    sprite = &entity->getComponent<SpriteComponent>();
}