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SFML Game Development book example game

Ceset (371)
Hi everyone

In game.h
ResourceHolder<Textures::ID, sf::Texture> mTextures;

I keep this file and ResourceHolder is a class which mainly focused on keeping the data of any resource such as sound, music and texture i guess:D. It is from SFML Game Development book.

And i use it in game.cpp like:
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Game::Game()
    :   mWindow(sf::VideoMode(640, 480), "SFML Application")
    ,   mTimePerFrame(sf::seconds(1.f / 60.f))
    ,   mTextures()
    ,   mPlayer()
    ,   mIsMovingLeft(false)
    ,   mIsMovingRight(false)
    ,   mIsMovingDown(false)
    ,   mIsMovingUp(false)
{
    mTextures.load(Textures::Airplane, "Media/Textures/Eagle.png");
    mTextures.load(Textures::Landscape, "Media/Textures/Landscape.png");
    mPlayer.setTexture(mTextures.get(Textures::Airplane));
    mPlayer.setPosition(100.f, 100.f);
}


And it gives me linker errors such as
D:\Projeler\sfmlSpaceShooter\classes\game.cpp:13: error: undefined reference to `ResourceHolder<Textures::ID, sf::Texture>::load(Textures::ID, std::string const&)'
.
.


Ant ResourceHolder class is like:
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template <typename Identifier, typename Resource>
class ResourceHolder
{
private:
    std::map<Identifier, std::unique_ptr<Resource>> mResourceMap;

public:
    void load(Identifier id, const std::string& filename);
    Resource& get(Identifier id);
    const Resource& get(Identifier id) const;
};


And the other code definitions goes the same way like this example one
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template <typename Identifier, typename Resource>
void ResourceHolder<Identifier, Resource>::load(Identifier id, const std::string& filename)
{
    std::unique_ptr<Resource> resource(new Resource());
    if(!resource->loadFromFile(filename))
        throw std::runtime_error("ResourceHolder::load - failed to load " + filename);

    auto inserted = mResourceMap.insert(std::make_pair(id, std::move(resource)));
    assert(inserted.second);
}


Like i said i am working from SFML Game Development book but it does not have its example codes as it teaches :(

What can i do to solve it.

Thanks in advance to all of you and sorry for this long message
Last edited on
Avilius (617)
Depending on your compiler you may have to put template function definitions in the same header file.
Ceset (371)
Thanks for the reply and answers. Problem solved.
cire (8284)
Like i said i am working from SFML Game Development book but it does not have its example codes as it teaches :(


https://github.com/LaurentGomila/SFML-Game-Development-Book

There will be some minor differences from the code in the book as the code has been improved with reader input since publishing.
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