检查 boost::container::vector::emplace_back 是如何实现的:http:
//www.boost.org/doc/libs/1_51_0/boost/container/vector.hpp
它使用 Boost.Preprocessor 自动生成采用不同数量参数的函数。它生成一些预定义数量的函数。
因此,您不必手动编写每个重载。相反,您只能编写一次您的模式。
例如:
#include <boost/preprocessor/iteration/local.hpp>
#include <boost/preprocessor/repetition/enum.hpp>
#include <boost/preprocessor/repetition/enum_trailing_params.hpp>
struct Entity
{
#define ENTITY_PP_PARAM_LIST(z, n, data) const BOOST_PP_CAT(P, n) & BOOST_PP_CAT(p, n)
#define ENTITY_PP_PARAM_PASS(z, n, data) BOOST_PP_CAT(p, n)
#define BOOST_PP_LOCAL_MACRO(n) \
template<typename GenericType BOOST_PP_ENUM_TRAILING_PARAMS(n, typename P) > \
void AddComponent(BOOST_PP_ENUM(n, ENTITY_PP_PARAM_LIST, _)) \
{ \
something=new GenericType(BOOST_PP_ENUM(n, ENTITY_PP_PARAM_PASS, _)); \
} \
/**/
#define BOOST_PP_LOCAL_LIMITS (0, 3)
#include BOOST_PP_LOCAL_ITERATE()
};
预处理扩展为:
struct Entity
{
template<typename GenericType >
void AddComponent()
{
something=new GenericType();
}
template<typename GenericType , typename P0 >
void AddComponent( const P0 & p0)
{
something=new GenericType( p0);
}
template<typename GenericType , typename P0 , typename P1 >
void AddComponent( const P0 & p0 , const P1 & p1)
{
something=new GenericType( p0 , p1);
}
template<typename GenericType , typename P0 , typename P1 , typename P2 >
void AddComponent( const P0 & p0 , const P1 & p1 , const P2 & p2)
{
something=new GenericType( p0 , p1 , p2);
}
};