c++ - 如何正确创建一个分为两个文件的模板类

Question

我一直在阅读 SFML 游戏开发一书，我想创建一个模板类。我将它分成 2 个文件:一个 .h 文件和一个 .inl 文件，如下所示:

// ResourceHolder.h
#ifndef _RES_HOLDER
#define _RES_HOLDER
#include <map>
#include <memory>
#include <SFML/Graphics.hpp>

namespace Resources
{
    enum ID {LandscapeTexture, AirplaneTexture, MissileTexture};

    template<typename Resource> 
    class ResourceHolder
    {   
    public:
        void load(Resources::ID id, const std::string& file);
        template<typename Parameter>
        void load(Resources::ID id, const std::string&file,
            const Parameter& param);

        Resource& get(Resources::ID id);
        const Resource& get(Resources::ID id) const;

    private:
        std::map<Resources::ID, std::unique_ptr<Resource>> mResourceMap;

    };
#include "ResourceHolder.inl"
};
#endif

.

//ResourceHolder.inl
template<typename Resource>
void Resources::ResourceHolder<Resource>::load(Resources::ID id,
                                  const std::string& file) 
{
    std::unique_ptr<Resource> resource(new Resource());
    if(!resource->loadFromFile(file))
        throw std::runtime_error("ResourceHolder::load failed to load : "+file);
    mResourceMap.insert(std::make_pair(id, std::move(resource)));
}

template<typename Resource>
template<typename Parameter>
void Resources::ResourceHolder<Resource>::load(Resources::ID id,
                                     const std::string& file,
                                     const Parameter& param) 
{
    std::unique_ptr<Resource> resource(new Resource());
    if(!resource->loadFromFile(file, param))
        throw std::runtime_error("ResourceHolder::load failed to load : "+file);
    mResourceMap.insert(std::make_pair(id, std::move(resource)));
}

template<typename Resource>
Resource& Resources::ResourceHolder<Resource>::get(Resources::ID id) 
{
    auto found = mResourceMap.find(id);
    return *found->second;
}

template<typename Resource>
const Resource& Resources::ResourceHolder<Resource>::get(Resources::ID id) const 
{
    auto found = mResourceMap.find(id);
    return *found->second;
}

但是当我尝试编译它时，我得到了这些错误:

1>  ResourceHolder.inl
1>d:\workspaces\resourceholder.inl(2): error C2143: syntax error : missing ';' before '<'
1>d:\workspaces\resourceholder.inl(2): error C2182: 'ResourceHolder' : illegal use of type 'void'
1>d:\workspaces\resourceholder.inl(2): error C2988: unrecognizable template declaration/definition
1>d:\workspaces\resourceholder.inl(2): error C2059: syntax error : '<'
1>d:\workspaces\resourceholder.inl(2): error C2039: 'load' : is not a member of '`global namespace''
1>d:\workspaces\resourceholder.inl(2): error C2653: 'Resources' : is not a class or namespace name
1>d:\workspaces\resourceholder.inl(3): error C2039: 'string' : is not a member of 'std'
1>d:\workspaces\resourceholder.inl(13): error C2039: 'load' : is not a member of '`global namespace''
1>d:\workspaces\resourceholder.inl(13): error C2653: 'Resources' : is not a class or namespace name
1>d:\workspaces\resourceholder.inl(14): error C2039: 'string' : is not a member of 'std'
1>d:\workspaces\resourceholder.inl(16): error C2143: syntax error : missing ';' before '{'
1>d:\workspaces\resourceholder.inl(16): error C2447: '{' : missing function header (old-style formal list?)
1>d:\workspaces\resourceholder.inl(24): error C2143: syntax error : missing ';' before '<'
1>d:\workspaces\resourceholder.inl(24): error C2040: 'ResourceHolder' : 'Resource &' differs in levels of indirection from 'int'
1>d:\workspaces\resourceholder.inl(24): error C2530: 'ResourceHolder' : references must be initialized
1>d:\workspaces\resourceholder.inl(24): error C2988: unrecognizable template declaration/definition
1>d:\workspaces\resourceholder.inl(24): error C2059: syntax error : '<'
1>d:\workspaces\resourceholder.inl(24): error C2039: 'get' : is not a member of '`global namespace''
1>d:\workspaces\resourceholder.inl(24): error C2653: 'Resources' : is not a class or namespace name
1>d:\workspaces\resourceholder.inl(31): error C2039: 'get' : is not a member of '`global namespace''
1>d:\workspaces\resourceholder.inl(31): error C2653: 'Resources' : is not a class or namespace name
1>d:\workspaces\resourceholder.inl(32): error C2143: syntax error : missing ';' before '{'
1>d:\workspaces\resourceholder.inl(32): error C2447: '{' : missing function header (old-style formal list?)

在过去的 2 个小时里，我一直在努力解决这个问题，我也曾尝试删除命名空间。

将模板类分隔在 .h 文件和 .inl 文件中的正确方法是什么？

编辑:

这似乎是正确的方法。出现错误是因为 VS studio 将我的 .inl 文件视为源文件并尝试对其进行编译。为了摆脱这个问题，我将它从我的项目中删除，然后再次添加。

Answer 1

我找到了答案。如果其他人遇到此问题是因为 Visual Studio 认为您的 .inl 文件是源文件并尝试编译它。

要解决这个问题，您需要将其从您的项目中移除并重新添加。如果在您的项目浏览器中显示的图标旁边有 2 个“+”，则无法编译。那是源文件的图标。