ref.hpp

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#pragma once
 
namespace flecs
{
 
template <typename T>
struct ref {
    ref() : world_(nullptr), ref_{} { }
 
    ref(world_t *world, entity_t entity, flecs::id_t id = 0)
        : ref_()
    {
        // the world we were called with may be a stage; convert it to a world
        // here if that is the case
        world_ = world ? const_cast<flecs::world_t *>(ecs_get_world(world))
            : nullptr;
        if (!id) {
            id = _::type<T>::id(world);
        }
 
#ifdef FLECS_DEBUG
        flecs::entity_t type = ecs_get_typeid(world, id);
        const flecs::type_info_t *ti = ecs_get_type_info(world, type);
        ecs_assert(ti && ti->size != 0, ECS_INVALID_PARAMETER,
            "cannot create ref to empty type");
#endif
        ref_ = ecs_ref_init_id(world_, entity, id);
    }
 
    ref(flecs::entity entity, flecs::id_t id = 0)
        : ref(entity.world(), entity.id(), id) { }
 
    T* operator->() {
        T* result = static_cast<T*>(ecs_ref_get_id(
            world_, &ref_, this->ref_.id));
 
        ecs_assert(result != NULL, ECS_INVALID_PARAMETER,
            "nullptr dereference by flecs::ref");
 
        return result;
    }
 
    T* get() {
        return static_cast<T*>(ecs_ref_get_id(
            world_, &ref_, this->ref_.id));
    }
 
    T* try_get() {
        if (!world_ || !ref_.entity) {
            return nullptr;
        }
 
        return get();
    }
 
    bool has() {
        return !!try_get();
    }
 
    operator bool() {
        return has();
    }
 
    flecs::entity entity() const;
 
    flecs::id component() const;
 
private:
    world_t *world_;
    flecs::ref_t ref_;
};
 
}