如何从boost :: geometry :: model :: point继承?

时间:2013-08-05 15:18:01

标签: c++ inheritance boost boost-geometry

我想继承bg::model::point以使用自己的功能扩展它。 * point * s应存储在rtree

以下最小示例无法编译我的派生点的使用(boost 1.54,gcc 4.7.2):

#include <boost/geometry.hpp>
#include <boost/geometry/geometries/point.hpp>
#include <boost/geometry/geometries/box.hpp>
#include <boost/geometry/index/rtree.hpp>
#include <iostream>
#include <boost/shared_ptr.hpp>

namespace bg = boost::geometry;
namespace bgi = boost::geometry::index;

namespace boost { namespace geometry { namespace index {

// apparently necessary:
template <typename Box>
struct indexable< boost::shared_ptr<Box> >
{
    typedef boost::shared_ptr<Box> V;

    typedef Box const& result_type;
    result_type operator()(V const& v) const { return *v; }
};

}}} // namespace boost::geometry::index


namespace { // anonymous namespace

// myPoint
template<typename CoordinateType, std::size_t DimensionCount, typename CoordinateSystem>
class myPoint : public bg::model::point<CoordinateType, DimensionCount, CoordinateSystem>{
public:
    void sayHello(void);
};

template<typename CoordinateType, std::size_t DimensionCount, typename CoordinateSystem>
void myPoint< CoordinateType, DimensionCount, CoordinateSystem >::sayHello() {
    std::cout<<"Hello!"<<std::endl;
}

} // end anonymous namespace

int main(void)
{
    typedef bg::model::point<float, 2, bg::cs::cartesian> point; // boost point version
    typedef myPoint<float, 2, bg::cs::cartesian> mypoint; // custom point version

    // create the rtree using default constructor
    bgi::rtree< boost::shared_ptr<point>, bgi::rstar<16, 4> > rtree; // that works
    bgi::rtree< boost::shared_ptr<mypoint>, bgi::rstar<16, 4> > myrtree; // that doesn't works

    return 0;
}

我如何从bg :: model :: point派生?或者,而不是继承,是否有更好的方法?

谢谢!

1 个答案:

答案 0 :(得分:3)

Boost.Geometry要求您的Point类型适应此处描述的Point Concept:

http://www.boost.org/doc/libs/1_54_0/libs/geometry/doc/html/geometry/reference/concepts/concept_point.html

您的派生类型myPoint也必须进行调整,因为它与您的基本类型不同,型号::指针&lt;&gt ;.这样做的原因是库允许调整遗留类并将它们用作几何图形而无需修改。

要使其适应,您必须使用其中一个注册宏或自己专门化所有必需的特征。除了评论中提到的例外,请参阅:

http://www.boost.org/doc/libs/1_54_0/libs/geometry/doc/html/geometry/examples.html

在第二个中,Point类型通过手动专业化所有必需特征进行调整,这是最灵活的方法。在你的情况下,这将是这样的:

namespace boost { namespace geometry { namespace traits {

template <typename C, std::size_t D, typename S>
struct tag< myPoint<C, D, S> >
{
    typedef point_tag type;
};
template <typename C, std::size_t D, typename S>
struct coordinate_type< myPoint<C, D, S> >
{
    typedef C type;
};
template <typename C, std::size_t D, typename S>
struct coordinate_system< myPoint<C, D, S> >
{
    typedef S type;
};
template <typename C, std::size_t D, typename S>
struct dimension< myPoint<C, D, S> >
{
    static const std::size_t value = D;
};
template <typename C, std::size_t D, typename S, std::size_t I>
struct access<myPoint<C, D, S>, I>
{
    static inline C get(myPoint<C, D, S> const& p)
    {
        return p.template get<I>();
    }

    static inline void set(myPoint<C, D, S> & p, C const& v)
    {
        p.template set<I>(v);
    }
};

}}}

只需在Point定义后粘贴它即可。