利用 C++ 元编程技术增强框架灵活性

#include <typeinfo>
#include <memory>

template<typename T> struct type_is { static constexpr bool value = false; };

template<> struct type_is<T> { static constexpr bool value = true; };

template<typename T> class ObjectPool {
    std::map<std::type_index, std::vector<std::shared_ptr<T>>> pool;

public:
    template<typename U, typename = std::enable_if_t<type_is<T>::value>>
    void create(U&& object) {
        pool[typeid(U)].emplace_back(std::make_shared<U>(std::forward<U>(object)));
    }

    template<typename U, typename = std::enable_if_t<type_is<T>::value>>
    std::shared_ptr<T> get() {
        auto& objects = pool[typeid(U)];
        if (objects.empty()) throw std::runtime_error("No objects in pool");
        auto object = std::move(objects.back());
        objects.pop_back();
        return object;
    }
};

ObjectPool<std::string> pool;
pool.create("Hello");
pool.create(5);
auto object = pool.get<std::string>();