libsigc++: Functors
Functors are copyable types that define operator()(). More...
Modules | |
Slots | |
Slots are type-safe representations of callback methods and functions. | |
mem_fun() | |
mem_fun() is used to convert a pointer to a method to a functor. | |
ptr_fun() | |
ptr_fun() is used to convert a pointer to a function to a functor. |
Classes | |
struct | sigc::functor_base |
A hint to the compiler. More... | |
struct | sigc::functor_trait< T_functor, I_derives_functor_base > |
Trait that specifies the return type of any type. More... |
Macros | |
#define | SIGC_FUNCTORS_HAVE_RESULT_TYPE |
Helper macro, if you want to mix user-defined and third party functors with libsigc++. | |
#define | SIGC_FUNCTOR_TRAIT(T_functor, T_return) |
Helper macro, if you want to mix user-defined and third party functors with libsigc++. | |
#define | SIGC_FUNCTORS_DEDUCE_RESULT_TYPE_WITH_DECLTYPE |
Helper macro, if you want to mix user-defined and third party functors with libsigc++. |
Functions | |
template<class T_action , class T_functor > | |
void | sigc::visit_each (const T_action& _A_action, const T_functor& _A_functor) |
This function performs a functor on each of the targets of a functor. | |
template <class T_type , class T_action , class T_functor > | |
void | sigc::visit_each_type (const T_action& _A_action, const T_functor& _A_functor) |
This function performs a functor on each of the targets of a functor limited to a restricted type. |
Detailed Description
Functors are copyable types that define operator()().
Types that define operator()() overloads with different return types are referred to as multi-type functors. Multi-type functors are only partially supported in libsigc++.
Closures are functors that store all information needed to invoke a callback from operator()().
Adaptors are functors that alter the signature of a functor's operator()().
libsigc++ defines numerous functors, closures and adaptors. Since libsigc++ is a callback library, most functors are also closures. The documentation doesn't distinguish between functors and closures.
The basic functor types libsigc++ provides are created with ptr_fun() and mem_fun() and can be converted into slots implicitly. The set of adaptors that ships with libsigc++ is documented in the Adaptors module.
If you want to mix user-defined and third party functors with libsigc++, and you want them to be implicitly convertible into slots, libsigc++ must know the result type of your functors. There are different ways to achieve that.
- Derive your functors from sigc::functor_base and place
typedef T_return result_type;
in the class definition. - Use the macro SIGC_FUNCTOR_TRAIT(T_functor,T_return) in namespace sigc. Multi-type functors are only partly supported.
- Use the macro SIGC_FUNCTORS_HAVE_RESULT_TYPE, if you want libsigc++ to assume that result_type is defined in all user-defined or third party functors, except those for which you specify a return type explicitly with SIGC_FUNCTOR_TRAIT().
- Use the macro SIGC_FUNCTORS_DEDUCE_RESULT_TYPE_WITH_DECLTYPE, if your compiler makes it possible. Functors with overloaded operator()() are not supported.
The last alterative makes it possible to construct a slot from a C++11 lambda expression with any return type. Example:
Macro Definition Documentation
#define SIGC_FUNCTOR_TRAIT | ( | T_functor, | |
T_return | |||
) |
Helper macro, if you want to mix user-defined and third party functors with libsigc++.
If you want to mix functors not derived from sigc::functor_base with libsigc++, and these functors don't define result_type
, use this macro inside namespace sigc to expose the return type of the functors like so:
#define SIGC_FUNCTORS_DEDUCE_RESULT_TYPE_WITH_DECLTYPE |
Helper macro, if you want to mix user-defined and third party functors with libsigc++.
If you want to mix functors not derived from sigc::functor_base with libsigc++, and your compiler can deduce the result type of the functor with the C++11 keyword decltype
, use this macro inside namespace sigc like so:
You can't use both SIGC_FUNCTORS_HAVE_RESULT_TYPE and SIGC_FUNCTORS_DEDUCE_RESULT_TYPE_WITH_DECLTYPE in the same compilation unit.
#define SIGC_FUNCTORS_HAVE_RESULT_TYPE |
Helper macro, if you want to mix user-defined and third party functors with libsigc++.
If you want to mix functors not derived from sigc::functor_base with libsigc++, and these functors define result_type
, use this macro inside namespace sigc like so:
You can't use both SIGC_FUNCTORS_HAVE_RESULT_TYPE and SIGC_FUNCTORS_DEDUCE_RESULT_TYPE_WITH_DECLTYPE in the same compilation unit.
Function Documentation
void sigc::visit_each | ( | const T_action & | _A_action, |
const T_functor & | _A_functor | ||
) |
This function performs a functor on each of the targets of a functor.
All unknown types just call _A_action on them. Add overloads that specialize the T_functor argument for your own functor types, so that subobjects get visited. This is needed to enable auto-disconnection support for your functor types.
- Example:
- struct some_functor{void operator()() {}some_possibly_sigc_trackable_derived_type some_data_member;some_other_functor_type some_other_functor;}namespace sigc{template <class T_action>const some_functor& _A_target){visit_each(_A_action, _A_target.some_data_member);visit_each(_A_action, _A_target.some_other_functor);}}