sol2/sol/property.hpp

// The MIT License (MIT)

// Copyright (c) 2013-2016 Rapptz, ThePhD and contributors

// Permission is hereby granted, free of charge, to any person obtaining a copy of
// this software and associated documentation files (the "Software"), to deal in
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// the Software, and to permit persons to whom the Software is furnished to do so,
// subject to the following conditions:

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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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#ifndef SOL_PROPERTY_HPP
#define SOL_PROPERTY_HPP

namespace sol {

	struct no_prop { };

	template <typename R, typename W>
	struct property_wrapper {
		typedef std::integral_constant<bool, !std::is_void<R>::value> can_read;
		typedef std::integral_constant<bool, !std::is_void<W>::value> can_write;
		typedef std::conditional_t<can_read::value, R, no_prop> Read;
		typedef std::conditional_t<can_write::value, W, no_prop> Write;
		Read read;
		Write write;

		template <typename Rx, typename Wx>
		property_wrapper(Rx&& r, Wx&& w) : read(std::forward<Rx>(r)), write(std::forward<Wx>(w)) {}
	};

	namespace property_detail {
		template <typename R, typename W>
		inline decltype(auto) property(std::true_type, R&& read, W&& write) {
			return property_wrapper<std::decay_t<R>, std::decay_t<W>>(std::forward<R>(read), std::forward<W>(write));
		}
		template <typename W, typename R>
		inline decltype(auto) property(std::false_type, W&& write, R&& read) {
			return property_wrapper<std::decay_t<R>, std::decay_t<W>>(std::forward<R>(read), std::forward<W>(write));
		}
		template <typename R>
		inline decltype(auto) property(std::true_type, R&& read) {
			return property_wrapper<std::decay_t<R>, void>(std::forward<R>(read), no_prop());
		}
		template <typename W>
		inline decltype(auto) property(std::false_type, W&& write) {
			return property_wrapper<void, std::decay_t<W>>(no_prop(), std::forward<W>(write));
		}
	} // property_detail

	template <typename F, typename G>
	inline decltype(auto) property(F&& f, G&& g) {
		using namespace sol;
		typedef lua_bind_traits<meta::unqualified_t<F>> left_traits;
		typedef lua_bind_traits<meta::unqualified_t<G>> right_traits;
		return property_detail::property(meta::boolean<(left_traits::arity < right_traits::arity)>(), std::forward<F>(f), std::forward<G>(g));
	}

	template <typename F>
	inline decltype(auto) property(F&& f) {
		using namespace sol;
		typedef lua_bind_traits<meta::unqualified_t<F>> left_traits;
		return property_detail::property(meta::boolean<(left_traits::arity == 0)>(), std::forward<F>(f));
	}

	// Allow someone to make a member variable readonly (const)
	template <typename R, typename T>
	auto readonly(R T::* v) {
		typedef const R C;
		return static_cast<C T::*>(v);
	}

} // sol

#endif // SOL_PROPERTY_HPP