C++ keywords: reflexpr (reflection TS)
Usage
- gets the member list of a class type, or the enumerator list of an enum type.
- gets the name of type and member.
- detects whether a data member is static or constexpr.
- detects whether member function is virtual, public, protected or private.
- get the row and column of the source code when the type defines.
Example
reflexpr provides us the meta info of the object via meta-object types. Note that std::reflect::get_data_members_t make programmers able to visit any class just like std::tuple.
#include <string>
#include <vector>
struct S {
int b;
std::string s;
std::vector<std::string> v;
};
// Reflection TS
#include <experimental/reflect>
using meta_S = reflexpr(S);
using mem = std::reflect::get_data_members_t<meta_S>;
using meta = std::reflect::get_data_members_t<mem>;
static_assert(std::reflect::is_public_v<meta>); // successful
int main() {}
We can also know the name info from reflexpr:
#include <string>
#include <string_view>
#include <iostream>
// Reflection TS
#include <experimental/reflect>
template <typename Tp>
constexpr std::string_view nameof() {
using TpInfo = reflexpr(Tp);
using aliased_Info = std::experimental::reflect::get_aliased_t<TpInfo>;
return std::experimental::reflect::get_name_v<aliased_Info>;
}
int main(){
std::cout << nameof<std::string>() << '\n';
static_assert(nameof<std::string>() == "basic_string"); // successful
}
This is an example of getting the scope of a type in the Reflection TS.
namespace Foo{
struct FooFoo{int FooFooFoo};
}
namespace Bar{
using BarBar = ::Foo::FooFoo;
}
using BarBarInfo = reflexpr(::Bar::BarBar);
using BarBarScope = ::std::experimental::reflect::get_scope_t<BarBarInfo>; // Bar, not Foo
struct Spam{int SpamSpam;};
struct Grok{
using GrokGrok = Spam::SpamSpam;
};
using GrokGrokInfo = reflexpr(::Grok::GrokGrok);
using GrokGrokScope = std::experimental::reflect::get_scope_t<GrokGrokInfo>; // Grok, not Spam
© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
https://en.cppreference.com/w/cpp/keyword/reflexpr
