libsigc++  2.99.4
Modules | Classes | Macros | Functions
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() Creates a functor from a pointer to a method.
 
 ptr_fun()
 ptr_fun() creates a functor from a pointer to a function.
 

Classes

class  sigc::can_deduce_result_type_with_decltype< T_functor >
 Helper class, to determine if decltype() can deduce the result type of a functor. More...
 
struct  sigc::functor_base
 A hint to the compiler. More...
 
struct  sigc::functor_trait< T_functor, I_derives_functor_base, I_can_use_decltype >
 Trait that specifies the return type of any type. More...
 
struct  sigc::visitor< T_functor >
 sigc::visitor<T_functor>::do_visit_each() performs a functor on each of the targets of a functor. More...
 

Macros

#define SIGC_FUNCTOR_TRAIT(T_functor, T_return)
 Helper macro, if you want to mix user-defined and third party functors with libsigc++. More...
 
#define SIGC_FUNCTORS_HAVE_RESULT_TYPE
 Helper macro, if you want to mix user-defined and third party functors with libsigc++. More...
 

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. More...
 
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. More...
 

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.

If all these ways to deduce the result type fail, void is assumed.

With libsigc++ versions before 2.6, the macro #SIGC_FUNCTORS_DEDUCE_RESULT_TYPE_WITH_DECLTYPE activated the test with decltype(). That macro is now unneccesary and deprecated.

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:

1 namespace sigc {
2  SIGC_FUNCTOR_TRAIT(first_functor_type, return_type_of_first_functor_type)
3  SIGC_FUNCTOR_TRAIT(second_functor_type, return_type_of_second_functor_type)
4  ...
5 }
#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:

1 namespace sigc { SIGC_FUNCTORS_HAVE_RESULT_TYPE }

Function Documentation

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.