How to controll shared ptr reference count? - c++

Question

I'm creating a Resource Manager for my game engine. Basically it have an unordered_map that stores the path of the resource as key and as value it stores the loaded resource.
This is the code responsible for loading assets.
std::shared_ptr<T> LoadAsset(const String& _path)
{
if (auto asset = m_assets.find(_path); asset != m_assets.end()) {
return std::static_pointer_cast<T>(asset->second);
}
auto asset = std::move(LoadAssetInternal(_path));
if (!asset) {
return nullptr;
}
m_assets[_path] = std::move(asset);
return std::static_pointer_cast<T>(m_assets[_path]);
}
The problem is that when I call the LoadAsset method, the returned shared_ptr variable always has 2 strong ref when I delete the variable holding the resource the ref count goes to 1 and the resource is never freed by the end of the program.
Exemple:
auto tex = LoadAsset<Texture>("Data/Textures/Foo.tga"); // Strong refs = 2
tex = nullptr; // Strong refs = 1 and the loaded Foo.tga is never freed.

Answer 1

Just create a function that runs at the end of your games main loop. Something like this
void PurgeAssets() {
for (auto i = m_assets.begin(); i != m_assets.end();) {
if (i->second.unique()) {
i = m_assets.erase(i);
}
else {
++i;
}
}
}