加大对结构和类融合序列类型和名称标识 [英] Boost fusion sequence type and name identification for structs and class
问题描述
我想使用升压融合为我的项目之一，我是搞清楚如何获得结构和类类型名和变量名。
I am trying to use boost fusion for one of my projects and I an figuring out how to get type names and variable names for structures and classes.
#include <typeinfo>
#include <string>
#include <iostream>
#include <boost/fusion/include/sequence.hpp>
#include <boost/fusion/include/algorithm.hpp>
#include <boost/fusion/include/vector.hpp>
#include <boost/fusion/include/adapt_struct.hpp>
#include <boost/fusion/include/adapt_adt.hpp>
#include <boost/lexical_cast.hpp>
using namespace boost::fusion;
struct Foo
{
int integer_value;
bool boolean_value;
};
class Bar
{
int integer_value;
bool boolean_value;
public:
Bar(int i_val, bool b_val):integer_value(i_val),boolean_value(b_val) {}
int get_integer_value() const { return integer_value; }
void set_integer_value(int i_val) { integer_value = i_val; }
bool get_boolean_value() const { return boolean_value; }
void set_boolean_value(bool b_val) { boolean_value = b_val; }
};
BOOST_FUSION_ADAPT_STRUCT(
Foo,
(int, integer_value)
(bool, boolean_value)
)
BOOST_FUSION_ADAPT_ADT(
Bar,
(int, int, obj.get_integer_value() , obj.set_integer_value(val))
(bool, bool, obj.get_boolean_value(), obj.set_boolean_value(val))
)
struct DisplayMembers
{
template <typename T>
void operator()(T& t) const {
std::cout << typeid(t).name() << " : " << boost::lexical_cast<std::string>(t) << std::endl;
}
};
int main(int argc, char *argv[])
{
struct Foo f = { 33, false};
for_each(f, DisplayMembers());
Bar b(34,true);
for_each(b, DisplayMembers());
return 0;
}
在上面的例子中，结果是
INT：33
BOOL：0
结构的boost ::融合::扩展:: adt_attribute_proxy：34
结构的boost ::融合::扩展:: adt_attribute_proxy：1
In the above example the result is int : 33 bool : 0 struct boost::fusion::extension::adt_attribute_proxy : 34 struct boost::fusion::extension::adt_attribute_proxy : 1
我要的结果作为
INT：integer_value：33
布尔：boolean_value：0
INT：integer_value：34
布尔：boolean_value：1
I want the result as int : integer_value : 33 bool : boolean_value : 0 int : integer_value : 34 bool : boolean_value : 1
推荐答案
有的boost ::融合::扩展:: struct_member_name＆LT; S，N ::值＆GT; 来访问名称
下面是我用一个通用的融合对象访问者：
Here's a generic fusion object visitor that I use:
namespace visitor {
template <typename Flavour, typename T> struct VisitorApplication;
namespace detail
{
template <typename V, typename Enable = void>
struct is_vector : boost::mpl::false_ { };
template <typename T>
struct is_vector<std::vector<T>, void> : boost::mpl::true_ { };
namespace iteration
{
// Iteration over a sequence
template <typename FusionVisitorConcept, typename S, typename N>
struct members_impl
{
// Type of the current member
typedef typename boost::fusion::result_of::value_at<S, N>::type current_t;
typedef typename boost::mpl::next<N>::type next_t;
typedef boost::fusion::extension::struct_member_name<S, N::value> name_t;
static inline void handle(FusionVisitorConcept& visitor, const S& s)
{
visitor.start_member(name_t::call());
VisitorApplication<FusionVisitorConcept, current_t>::handle(visitor, boost::fusion::at<N>(s));
visitor.finish_member(name_t::call());
members_impl<FusionVisitorConcept, S, next_t>::handle(visitor, s);
}
};
// End condition of sequence iteration
template <typename FusionVisitorConcept, typename S>
struct members_impl<FusionVisitorConcept, S, typename boost::fusion::result_of::size<S>::type>
{
static inline void handle(FusionVisitorConcept const&, const S&) { /*Nothing to do*/ }
};
// Iterate over struct/sequence. Base template
template <typename FusionVisitorConcept, typename S>
struct Struct : members_impl<FusionVisitorConcept, S, boost::mpl::int_<0>> {};
} // iteration
template <typename FusionVisitorConcept, typename T>
struct array_application
{
typedef array_application<FusionVisitorConcept, T> type;
typedef typename T::value_type value_type;
static inline void handle(FusionVisitorConcept& visitor, const T& t)
{
visitor.empty_array();
for (auto& el : t)
VisitorApplication<FusionVisitorConcept, value_type>::handle(visitor, el);
}
};
template <typename FusionVisitorConcept, typename T>
struct struct_application
{
typedef struct_application<FusionVisitorConcept, T> type;
static inline void handle(FusionVisitorConcept& visitor, const T& t)
{
visitor.empty_object();
iteration::Struct<FusionVisitorConcept, T>::handle(visitor, t);
}
};
template <typename FusionVisitorConcept, typename T, typename Enable = void>
struct value_application
{
typedef value_application<FusionVisitorConcept, T> type;
static inline void handle(FusionVisitorConcept& visitor, const T& t) {
visitor.value(t);
}
};
template <typename FusionVisitorConcept, typename T>
struct value_application<FusionVisitorConcept, boost::optional<T> >
{
typedef value_application<FusionVisitorConcept, boost::optional<T> > type;
static inline void handle(FusionVisitorConcept& visitor, const boost::optional<T>& t) {
if (t)
VisitorApplication<FusionVisitorConcept, T>::handle(visitor, *t);
else
; // perhaps some default action?
}
};
template <typename FusionVisitorConcept, typename T>
struct select_application
{
typedef
//typename boost::mpl::eval_if<boost::is_array<T>, boost::mpl::identity<array_application<FusionVisitorConcept, T>>,
typename boost::mpl::eval_if<detail::is_vector<T>, boost::mpl::identity<array_application <FusionVisitorConcept, T>>,
typename boost::mpl::eval_if<boost::fusion::traits::is_sequence<T>, boost::mpl::identity<struct_application<FusionVisitorConcept, T>>,
boost::mpl::identity<value_application<FusionVisitorConcept, T>>
> >::type type;
};
} // detail
template <typename FusionVisitorConcept, typename T>
struct VisitorApplication : public detail::select_application<FusionVisitorConcept, T>::type
{
};
}
template <typename FusionVisitorConcept, typename T>
void apply_fusion_visitor(FusionVisitorConcept& visitor, T const& o)
{
visitor::VisitorApplication<FusionVisitorConcept, T>::handle(visitor, o);
}
您可以通过提供访客使用它，例如对XML般的输出：
You can use it by supplying a visitor, e.g. for xml-like output:
struct DisplayMemberVisitor {
typedef std::string result_type;
DisplayMemberVisitor() { ss << std::boolalpha; }
std::string complete() { return ss.str(); }
void start_member (const char* name) {
ss << "<" << name << ">";
}
void finish_member(const char* name) {
ss << "</" << name << ">";
}
template <typename T> void value(T const& value) {
ss << value;
}
void empty_object() { }
void empty_array() { }
private:
std::stringstream ss;
};
看它的 住在Coliru 在哪里（包括一些调试输出），它打印：
See it Live On Coliru where (including some debug output) it prints:
<$c$c><integer_value>33</integer_value><boolean_value>false</boolean_value><integer_value>34</integer_value><boolean_value>true</boolean_value>
注意的ADT适应宏观不包括名称（因为没有可用）。你可能很容易使宏观 FUSION_ADAPT_KEYD_ADT 也接受的名称，并生成相关专业的boost ::融合::扩展:: struct_member_name 。
Note that the ADT adaptation macro doesn't include a name (because none is available). You can probably quite easily make a macro FUSION_ADAPT_KEYD_ADT that also accepts a name and generates the relevant specializations of boost::fusion::extension::struct_member_name.
下面是一个简单的方法，显示需要什么样的工作少量工作要做。
Here's a simplistic approach that shows what little amount of work needs to be done.
#define MY_ADT_MEMBER_NAME(CLASSNAME, IDX, MEMBERNAME) \
namespace boost { namespace fusion { namespace extension { \
template <> struct struct_member_name<CLASSNAME, IDX> { typedef char const *type; static type call() { return #MEMBERNAME; } \
}; } } }
MY_ADT_MEMBER_NAME(Bar, 0, integer_value)
MY_ADT_MEMBER_NAME(Bar, 1, boolean_value)
这定义一个宏避免大部分的重复。如果你是一个BOOST_PP whizkid你可以以某种方式编织这个成 adt_ex.hpp ¹各种各样的头，所以你可以代替说：
This defines a macro to avoid most of the repetition. If you are a BOOST_PP whizkid you could somehow weave this into an adt_ex.hpp¹ header of sorts, so you could instead say:
BOOST_FUSION_ADAPT_ADT(Bar, // NOTE THIS PSEUDO-CODE
(integer_value, int, int, obj.get_integer_value(), obj.set_integer_value(val))
(boolean_value, bool, bool, obj.get_boolean_value(), obj.set_boolean_value(val)))
有关现在，这里的ADT适应伎俩<大骨节病> 住在Coliru
For now here's the ADT adapted trick Live On Coliru
在¹你感兴趣的情况下，这里的$ P $的压缩包ppared adt_ex树（下降alongsize adt.hpp）的 adt_ex.tgz 为出发点。这只是ADT *而是改名为adt_ex宏和头警卫*
¹ in case you're interested, here's a tarball of a prepared adt_ex tree (drop in alongsize adt.hpp): adt_ex.tgz as a starting point. It's just adt* but with macros and header guards renamed to adt_ex*
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