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