WrappedWithOwnerDecorator.h

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#pragma once
#include <memory>
 
namespace catapult { namespace utils {
 
    template<typename THandler>
    class WrappedWithOwnerDecorator {
    public:
        template<typename TOwner>
        WrappedWithOwnerDecorator(const std::shared_ptr<TOwner>& pOwner, THandler handler)
                : m_pOwner(pOwner)
                , m_handler(std::move(handler))
        {}
 
    public:
        template<typename... TArgs>
        auto operator()(TArgs&& ...args) const {
            return m_handler(std::forward<TArgs>(args)...);
        }
 
        const std::shared_ptr<const void>& owner() const {
            return m_pOwner;
        }
 
    protected:
        std::shared_ptr<const void> m_pOwner; // owner must be destroyed last in case handler holds raw reference(s) to it
        THandler m_handler;
    };
 
    template<typename THandler>
    class ResettableWrappedWithOwnerDecorator : public WrappedWithOwnerDecorator<THandler> {
    public:
        template<typename TOwner>
        ResettableWrappedWithOwnerDecorator(const std::shared_ptr<TOwner>& pOwner, THandler handler)
                : WrappedWithOwnerDecorator<THandler>(pOwner, std::move(handler))
        {}
 
    public:
        void reset() {
            using BaseType = WrappedWithOwnerDecorator<THandler>;
            auto empty = decltype(BaseType::m_handler)();
            BaseType::m_handler.swap(empty);
            BaseType::m_pOwner.reset();
        }
    };
}}