C++ 编译错误和命名空间

发布于 2024-10-29 16:27:09 字数 1064 浏览 8 评论 0原文

这是出现错误的整个代码：

Engine.h

#ifndef ENGINE_H
#define ENGINE_H

#include "DXManager.h"

namespace XEngine
{
    class Engine
    {
    };
}

#endif

DXManager.h

#ifndef DX_MANAGER_H
#define DX_MANAGER_H



namespace XEngine
{
    class Engine; // forward declaration

    class DXManager
    {
    public:
        void run(Engine *engine);
    };
}

#endif

DXManager.cpp

#include <iostream>

#include "Engine.h"
#include "DXManager.h"

using namespace XEngine;

void DXManager::run(Engine *engine)
{
    std::cout<<"DXManager::run"<<std::endl;
}

通过这 30 行代码，我得到了 20 行错误如：

'XEngine' : a namespace with this name does not exist
'XEngine' : a symbol with this name already exists and therefore this name cannot be used as a namespace name
syntax error : identifier 'Engine'

显然，我在这里遗漏了一些重要的东西。我做错了什么？

注意：我知道循环依赖是一件坏事，但在我的特定情况下，我相信它是相关的。

原文

Here's the whole code getting the errors:

Engine.h

#ifndef ENGINE_H
#define ENGINE_H

#include "DXManager.h"

namespace XEngine
{
    class Engine
    {
    };
}

#endif

DXManager.h

#ifndef DX_MANAGER_H
#define DX_MANAGER_H



namespace XEngine
{
    class Engine; // forward declaration

    class DXManager
    {
    public:
        void run(Engine *engine);
    };
}

#endif

DXManager.cpp

#include <iostream>

#include "Engine.h"
#include "DXManager.h"

using namespace XEngine;

void DXManager::run(Engine *engine)
{
    std::cout<<"DXManager::run"<<std::endl;
}

With these 30 lines of code, I'm getting 20 errors like:

'XEngine' : a namespace with this name does not exist
'XEngine' : a symbol with this name already exists and therefore this name cannot be used as a namespace name
syntax error : identifier 'Engine'

Clearly, I'm missing something important here. What am I doing wrong?

note: I am aware that circular dependency is a bad thing, but in my particular case I believe that it is relevant.

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日暮斜阳 2024-11-05 16:27:09

在 DXManager.cpp 中，您不仅仅使用命名空间 XEngine 中的一些名称。您在该命名空间中定义该函数。

所以一定是：

DXManager.cpp

#include <iostream>

#include "Engine.h"
#include "DXManager.h"

namespace XEngine {

void DXManager::run(Engine *engine)
{
    std::cout<<"DXManager::run"<<std::endl;
}

}

AFAIK 一些编译器（如 MSVC）也处理 using 变体。
但这是不正确的，因为您的语法尝试定义函数 ::DXManager::run - 而不是您想要定义的 ::XEngine::DXManager::run 。

In DXManager.cpp you are not just using some names from namespace XEngine. You define the function in that namespace.

So must be:

DXManager.cpp

#include <iostream>

#include "Engine.h"
#include "DXManager.h"

namespace XEngine {

void DXManager::run(Engine *engine)
{
    std::cout<<"DXManager::run"<<std::endl;
}

}

AFAIK some of the compilers (like MSVC) process using variant too.
But it is not correct because your syntax tries to define function ::DXManager::run - not ::XEngine::DXManager::run you intend to define.

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