TemplateHelpers.hh File Reference

#include <type_traits>

Go to the source code of this file.

Classes
struct	ConstCompatible< To, From >
	Contains a static constexpr field named value which will be true if the type From has a const-quality less than or equal to the type To. More...
struct	ConstCompatible< To, const From >
struct	Empty
	Useful as a blank placeholder in template metaprogramming. More...
struct	type< T >
	This can be used to turn a type into a function argument, which is useful for template metaprogramming. More...

Namespaces
	ignition
	ignition::physics

Macros
#define	IGN_PHYSICS_CREATE_SELECTOR(X)
	Use this macro to create an API "selector" for a custom class. More...

Typedefs
template<typename... >
using	void_t = void

Macro Definition Documentation

IGN_PHYSICS_CREATE_SELECTOR

#define IGN_PHYSICS_CREATE_SELECTOR

(

X

)

Value:

template<typename InFeature> \
  struct Select ## X \
  { \
    template<typename F, typename PolicyT, typename FeaturesT, \
             typename = ::void_t<>> \
    struct Implementation \
    { \
      using type = ::Empty; \
    }; \
    \
    template<typename F, typename PolicyT, typename FeaturesT> \
    struct Implementation<F, PolicyT, FeaturesT, \
                          ::void_t< \
                              typename F::template X <PolicyT, FeaturesT>>> \
    { \
      using type = typename F::template X <PolicyT, FeaturesT>; \
    }; \
    \
    template <typename PolicyT, typename FeaturesT> \
    using type = typename Implementation<InFeature, PolicyT, FeaturesT>::type; \
  };

Use this macro to create an API "selector" for a custom class.

Features may define APIs for class types that are not anticipated ahead of time by the ign-physics library. When aggregating the API for that class from a set of features, the Aggregator must be given a Selector that can ignore features that don't mention the class (or else a compilation failure would occur).

This macro creates a class that uses SFINAE (https://en.wikipedia.org/wiki/Substitution_failure_is_not_an_error) to ignore features that don't define an API for the class of interest (X). When using this macro, pass in the name of the class that you want the selector to look for. If the class name is X, then this will create a selector named SelectX. E.g. IGN_PHYSICS_CREATE_SELECTOR(RevoluteJoint) will create a class named SelectRevoluteJoint which can be passed to an Aggregator to extract the RevoluteJoint API from a list of features.