glibmm: Glib::WeakRef< T_CppObject > Class Template Reference

glibmm 2.51.2

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Glib::WeakRef< T_CppObject > Class Template Reference

WeakRef<> is a weak reference smartpointer. More...

`#include <glibmm/weakref.h>`

## Public Member Functions
| WeakRef () noexcept
| Default constructor. More...
| WeakRef (const WeakRef& src) noexcept
| Copy constructor. More...
| WeakRef (WeakRef&& src) noexcept
| Move constructor. More...
template<typename T_CastFrom >
| WeakRef (const WeakRef< T_CastFrom >& src) noexcept
| Copy constructor from different, but castable type. More...
template<typename T_CastFrom >
| WeakRef (WeakRef< T_CastFrom >&& src) noexcept
| Move constructor from different, but castable type. More...
template<typename T_CastFrom >
| WeakRef (const RefPtr< T_CastFrom >& src) noexcept
| Constructor from a RefPtr of the same or a castable type. More...
| ~WeakRef () noexcept
| Destructor. More...
void | swap (WeakRef& other) noexcept
| Swap the contents of two WeakRef<>. More...
WeakRef& | operator= (const WeakRef& src) noexcept
| Copy assignment operator. More...
WeakRef& | operator= (WeakRef&& src) noexcept
| Move assignment operator. More...
template<typename T_CastFrom >
WeakRef& | operator= (const WeakRef< T_CastFrom >& src) noexcept
| Copy assignment from different, but castable type. More...
template<typename T_CastFrom >
WeakRef& | operator= (WeakRef< T_CastFrom >&& src) noexcept
| Move assignment from different, but castable type. More...
template<typename T_CastFrom >
WeakRef& | operator= (const RefPtr< T_CastFrom >& src) noexcept
| Assignment from a RefPtr of the same or a castable type. More...
| operator bool () const noexcept
| Test whether the WeakRef<> points to any underlying instance. More...
RefPtr< T_CppObject > | get () const noexcept
| Create a strong reference to the underlying object. More...
void | reset () noexcept
| Make this WeakRef empty. More...

## Static Public Member Functions
template<typename T_CastFrom >
static WeakRef | cast_dynamic (const WeakRef< T_CastFrom >& src) noexcept
| Dynamic cast to derived class. More...
template<typename T_CastFrom >
static WeakRef | cast_static (const WeakRef< T_CastFrom >& src) noexcept
| Static cast to derived class. More...
template<typename T_CastFrom >
static WeakRef | cast_const (const WeakRef< T_CastFrom >& src) noexcept
| Cast to non-const. More...

## Related Functions
(Note that these are not member functions.)
template<class T_CppObject >
void | swap (WeakRef< T_CppObject >& lhs, WeakRef< T_CppObject >& rhs) noexcept
| Swap the contents of two WeakRef<>. More...

## Detailed Description

### template<typename T_CppObject>
class Glib::WeakRef< T_CppObject >

WeakRef<> is a weak reference smartpointer.

WeakRef can store a pointer to any class that is derived from Glib::ObjectBase, and whose reference() method is noexcept. In glibmm and gtkmm, that is anything derived from Glib::ObjectBase.

Unlike a RefPtr, a WeakRef does not contribute to the reference counting of the underlying object.

Since glibmm 2.46:

## Constructor & Destructor Documentation

template <typename T_CppObject >

Glib::WeakRef< T_CppObject >::WeakRef | ( |  | ) |
| inlinenoexcept

Default constructor.

Create an empty weak reference.

template <typename T_CppObject >

Glib::WeakRef< T_CppObject >::WeakRef | ( | const WeakRef< T_CppObject >& | src | ) |
| inlinenoexcept

Copy constructor.

template <typename T_CppObject >

Glib::WeakRef< T_CppObject >::WeakRef | ( | WeakRef< T_CppObject >&& | src | ) |
| inlinenoexcept

Move constructor.

template <typename T_CppObject >
template <typename T_CastFrom >

Glib::WeakRef< T_CppObject >::WeakRef | ( | const WeakRef< T_CastFrom >& | src | ) |
| inlinenoexcept

Copy constructor from different, but castable type.

template <typename T_CppObject >
template <typename T_CastFrom >

Glib::WeakRef< T_CppObject >::WeakRef | ( | WeakRef< T_CastFrom >&& | src | ) |
| inlinenoexcept

Move constructor from different, but castable type.

template <typename T_CppObject >
template <typename T_CastFrom >

Glib::WeakRef< T_CppObject >::WeakRef | ( | const RefPtr< T_CastFrom >& | src | ) |
| inlinenoexcept

Constructor from a RefPtr of the same or a castable type.

Create a weak reference from a RefPtr of the same or a castable type. If the RefPtr references nothing, an empty weak reference will be constructed.

template <typename T_CppObject >

Glib::WeakRef< T_CppObject >::~WeakRef | ( |  | ) |
| inlinenoexcept

Destructor.

## Member Function Documentation

template <typename T_CppObject >
template <typename T_CastFrom >

static WeakRef Glib::WeakRef< T_CppObject >::cast_const | ( | const WeakRef< T_CastFrom >& | src | ) |
| inlinestaticnoexcept

Cast to non-const.

The WeakRef can't be cast with the usual notation so instead you can use

ptr_nonconst = Glib::WeakRef<NonConstType>::cast_const(ptr_const);
template <typename T_CppObject >
template <typename T_CastFrom >

static WeakRef Glib::WeakRef< T_CppObject >::cast_dynamic | ( | const WeakRef< T_CastFrom >& | src | ) |
| inlinestaticnoexcept

Dynamic cast to derived class.

The WeakRef can't be cast with the usual notation so instead you can use

ptr_derived = Glib::WeakRef<Derived>::cast_dynamic(ptr_base);
template <typename T_CppObject >
template <typename T_CastFrom >

static WeakRef Glib::WeakRef< T_CppObject >::cast_static | ( | const WeakRef< T_CastFrom >& | src | ) |
| inlinestaticnoexcept

Static cast to derived class.

The WeakRef can't be cast with the usual notation so instead you can use

ptr_derived = Glib::WeakRef<Derived>::cast_static(ptr_base);
template <typename T_CppObject >

RefPtr<T_CppObject> Glib::WeakRef< T_CppObject >::get | ( |  | ) | const
| inlinenoexcept

Create a strong reference to the underlying object.

This is a thread-safe way to acquire a strong reference to the underlying object. If the WeakRef is empty, the returned RefPtr will reference nothing.

template <typename T_CppObject >

Glib::WeakRef< T_CppObject >::operator bool | ( |  | ) | const
| inlineexplicitnoexcept

Test whether the WeakRef<> points to any underlying instance.

Mimics usage of ordinary pointers:

if (ptr)
do_something();

In a multi-threaded program a `true` return value can become obsolete at any time, even before the caller has a chance to test it, because the underlying instance may lose its last reference in another thread. Use get() if this is not acceptable.

template <typename T_CppObject >

WeakRef& Glib::WeakRef< T_CppObject >::operator= | ( | const WeakRef< T_CppObject >& | src | ) |
| inlinenoexcept

Copy assignment operator.

template <typename T_CppObject >

WeakRef& Glib::WeakRef< T_CppObject >::operator= | ( | WeakRef< T_CppObject >&& | src | ) |
| inlinenoexcept

Move assignment operator.

template <typename T_CppObject >
template <typename T_CastFrom >

WeakRef& Glib::WeakRef< T_CppObject >::operator= | ( | const WeakRef< T_CastFrom >& | src | ) |
| inlinenoexcept

Copy assignment from different, but castable type.

template <typename T_CppObject >
template <typename T_CastFrom >

WeakRef& Glib::WeakRef< T_CppObject >::operator= | ( | WeakRef< T_CastFrom >&& | src | ) |
| inlinenoexcept

Move assignment from different, but castable type.

template <typename T_CppObject >
template <typename T_CastFrom >

WeakRef& Glib::WeakRef< T_CppObject >::operator= | ( | const RefPtr< T_CastFrom >& | src | ) |
| inlinenoexcept

Assignment from a RefPtr of the same or a castable type.

template <typename T_CppObject >

void Glib::WeakRef< T_CppObject >::reset | ( |  | ) |
| inlinenoexcept

Make this WeakRef empty.

template <typename T_CppObject >

void Glib::WeakRef< T_CppObject >::swap | ( | WeakRef< T_CppObject >& | other | ) |
| inlinenoexcept

Swap the contents of two WeakRef<>.

## Friends And Related Function Documentation

template <class T_CppObject >

void swap | ( | WeakRef< T_CppObject >& | lhs,
|  | WeakRef< T_CppObject >& | rhs
| ) |  |
| related

Swap the contents of two WeakRef<>.