clang++ -std=c++11 -o comps comps.cpp

comps.cpp

#include <stdio.h>
#include <typeinfo>
#include <unordered_map>

class Foo {
public:
    void dump() { printf("Hello, foo!\n"); }
};

class Bar {
public:
    void dump() { printf("Hello, bar!\n"); }
};

class Entity { // {{{
public:
    template<typename T, typename... Args>
    void addComponent(Args&... args);

    template<typename T>
    T* getComponent();

private:
    std::unordered_map<const std::type_info*, void*> components_;
}; // }}}

// {{{ template inlines
template<typename T, typename... Args>
void Entity::addComponent(Args&... args)
{
    components_[&typeid(T)] = new T(args...);
}

template<typename T>
T* Entity::getComponent()
{
    auto i = components_.find(&typeid(T));
    if (i != components_.end())
        return static_cast<T*>(i->second);

    return nullptr;
}
// }}}

int main() {
    Entity e;
    e.addComponent<Foo>();
    e.addComponent<Bar>();

    Foo* foo = e.getComponent<Foo>();
    Bar* bar = e.getComponent<Bar>();

    foo->dump();
    bar->dump();
}