libsigc++: sigc::adapts< T_functor > Struct Template Reference

libsigc++ 3.0.0

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sigc::adapts< T_functor > Struct Template Reference
Adaptors

Base type for adaptors. More...

`#include <sigc++/adaptors/adapts.h>`

Inheritance diagram for sigc::adapts< T_functor >:
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## Public Member Functions
| adapts (const T_functor& functor)
| Constructs an adaptor that wraps the passed functor. More...

## Public Attributes
adaptor_type | functor_
| Adaptor that is invoked from operator()(). More...

## Detailed Description

### template<typename T_functor>
struct sigc::adapts< T_functor >

Base type for adaptors.

sigc::adapts wraps adaptors, functors, function pointers and class methods. It contains a single member functor which is always a sigc::adaptor_base. The adaptor_type alias defines the exact type that is used to store the adaptor, functor, function pointer or class method passed into the constructor. It differs from T_functor unless T_functor inherits from sigc::adaptor_base.

Example of a simple adaptor:
  namespace my_ns
  {
  template <typename T_functor>
  struct my_adaptor : public sigc::adapts<T_functor>
  {
  //
  decltype(auto)
  operator()() const;
  //
  template <typename T_arg1>
  decltype(auto)
  operator()(T_arg1 arg1) const;
  //
  template <typename T_arg1, typename T_arg2>
  decltype(auto)
  operator()(T_arg1 arg1, T_arg2 arg2) const;
  //
  // Constructs a my_adaptor object that wraps the passed functor.
  // Initializes adapts<T_functor>::functor_, which is invoked from operator()().
  explicit my_adaptor(const T_functor& functor)
  : sigc::adapts<T_functor>(functor) {}
  };
  } // end namespace my_ns
  //
  // Specialization of sigc::visitor for my_adaptor.
  namespace sigc
  {
  template <typename T_functor>
  struct visitor<my_ns::my_adaptor<T_functor> >
  {
  template <typename T_action>
  static void do_visit_each(const T_action& action,
  const my_ns::my_adaptor<T_functor>& target)
  {
  sigc::visit_each(action, target.functor_);
  }
  };
  } // end namespace sigc

If you implement your own adaptor, you must also provide your specialization of sigc::visitor<>::do_visit_each<>() that will forward the call to the functor(s) your adapter is wrapping. Otherwise, pointers stored within the functor won't be invalidated when a sigc::trackable object is destroyed and you can end up executing callbacks on destroyed objects.

Your specialization of sigc::visitor<> must be in namespace sigc.

## Constructor & Destructor Documentation

template <typename T_functor>

sigc::adapts< T_functor >::adapts | ( | const T_functor & | functor | ) |
| inlineexplicit

Constructs an adaptor that wraps the passed functor.

Parameters

  functor | Functor to invoke from operator()().

## Member Data Documentation

template <typename T_functor>

adaptor_type sigc::adapts< T_functor >::functor_
| mutable

Adaptor that is invoked from operator()().