55 lines
1.4 KiB
C++
55 lines
1.4 KiB
C++
/*
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* Copyright (C) 2013 Alec Thomas <alec@swapoff.org>
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* All rights reserved.
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*
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* This software is licensed as described in the file COPYING, which
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* you should have received as part of this distribution.
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*
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* Author: Alec Thomas <alec@swapoff.org>
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*/
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#pragma once
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#include "entityx/System.h"
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#include "entityx/Event.h"
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#include "entityx/Entity.h"
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namespace entityx {
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namespace deps {
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/**
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* An entityx::System for declaring component dependencies.
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*
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* eg. To declare that a `Physics` component must always be paired with `Position`
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* and `Direction` components:
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*
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* system_manager->add<Dependency<Physics, Position, Direction>>();
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*/
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template <typename C, typename ... Deps>
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class Dependency : public System<Dependency<C, Deps...>>, public Receiver<Dependency<C, Deps...>> {
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public:
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void receive(const ComponentAddedEvent<C> &event) {
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assign<Deps...>(event.entity);
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}
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void configure(EventManager &events) override {
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events.subscribe<ComponentAddedEvent<C>>(*this);
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}
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void update(EntityManager &entities, EventManager &events, TimeDelta dt) override {}
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private:
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template <typename D>
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void assign(Entity entity) {
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if (!entity.component<D>()) entity.assign<D>();
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}
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template <typename D, typename D1, typename ... Ds>
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void assign(Entity entity) {
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assign<D>(entity);
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assign<D1, Ds...>(entity);
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}
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};
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} // namespace deps
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} // namespace entityx
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