composite_param.hpp

Go to the documentation of this file.

#pragma once
 
#include <helios/ecs/schedule/system_local_data.hpp>
#include <helios/ecs/system/access_decl.hpp>
#include <helios/ecs/world.hpp>
 
namespace helios::ecs {
 
/**
 * @brief Helper for implementing `SystemParamTraits` on aggregate parameters.
 * @details Inherit from this type in a `SystemParamTraits` specialization when
 * every field is itself a system parameter. Field types in `Fields...` must
 * match the aggregate's member types exactly.
 * @tparam Param Aggregate parameter type
 * @tparam Fields System parameter types for each aggregate field, in order
 */
template <typename Param, typename... Fields>
struct CompositeSystemParam {
  /**
   * @brief Constructs the aggregate from each field's `Make`.
   * @param world World instance
   * @param data Per-system local data
   * @param policy Compiled access policy for the system
   * @return Constructed aggregate parameter
   */
  static Param Make(World& world, SystemLocalData& data,
                    const AccessPolicy& policy) {
    return Param{SystemParamTraits<Fields>::Make(world, data, policy)...};
  }
 
  /**
   * @brief Registers access for all fields.
   * @param builder Access policy builder
   */
  static constexpr void RegisterAccess(AccessPolicyBuilder& builder) {
    RegisterParamAccess<Fields...>(builder);
  }
};
 
}  // namespace helios::ecs