WeakPtr< T >

#include <Ultralight/RefPtr.h>

Overview

template<typename T>
class ultralight::WeakPtr< T >

A weak (non-owning) smart pointer that observes a WeakRefCounted object.

A WeakPtr does not keep its object alive. Use Lock() to atomically obtain a strong RefPtr to the object; the result is null if the object has already been destroyed.

Usage

RefPtr<Bitmap> bitmap = Bitmap::Create(100, 100, BitmapFormat::BGRA8_UNORM_SRGB);
WeakPtr<Bitmap> weak(bitmap);
 
if (RefPtr<Bitmap> strong = weak.Lock()) {
  // The object is alive and stays alive while 'strong' is in scope.
}

Thread-safe: WeakPtr instances can be created, copied, and destroyed on any thread, and Lock() is race-free against concurrent destruction of the object.

Note

T must derive from WeakRefCounted; using WeakPtr with a plain RefCounted type is a compile error.

Note

Only construct a WeakPtr from a fully-constructed object: never from this inside a constructor.

Public Member Functions
constexpr	WeakPtr ()
	Construct a null WeakPtr.
	WeakPtr (std::nullptr_t)
	Construct a null WeakPtr.
template<typename U>
	WeakPtr (const RefPtr< U > &strong)
	Construct a WeakPtr observing the object held by a RefPtr (may be null).
template<typename U>
	WeakPtr (U *instance)
	Construct a WeakPtr observing a raw pointer (may be null).
	WeakPtr (const WeakPtr &other)
	Copy constructor.
	WeakPtr (WeakPtr &&other)
	Move constructor.
	~WeakPtr ()
WeakPtr &	operator= (const WeakPtr &other)
WeakPtr &	operator= (WeakPtr &&other)
WeakPtr &	operator= (std::nullptr_t)
template<typename U>
WeakPtr &	operator= (const RefPtr< U > &strong)
RefPtr< T >	Lock () const
	Atomically take a strong reference to the observed object.
bool	Expired () const
	Whether the observed object has been destroyed (or this WeakPtr is null).
void	Reset ()
	Stop observing the object and become a null WeakPtr.
void	swap (WeakPtr &other)
	Exchanges the observed objects of *this and other.

Friends
template<typename U>
class	WeakPtr

Constructor & Destructor Documentation

WeakPtr() [1/6]

template<typename T>

WeakPtr ( )

inlineconstexpr

Construct a null WeakPtr.

WeakPtr() [2/6]

template<typename T>

WeakPtr ( std::nullptr_t )

inline

Construct a null WeakPtr.

WeakPtr() [3/6]

template<typename T>

template<typename U>

WeakPtr ( const RefPtr< U > & strong )

inline

Construct a WeakPtr observing the object held by a RefPtr (may be null).

WeakPtr() [4/6]

template<typename T>

template<typename U>

WeakPtr ( U * instance )

inlineexplicit

Construct a WeakPtr observing a raw pointer (may be null).

The object must currently be alive: the caller (or another owner) must hold a strong reference to it.

WeakPtr() [5/6]

template<typename T>

WeakPtr ( const WeakPtr< T > & other )

inline

Copy constructor.

WeakPtr() [6/6]

template<typename T>

WeakPtr ( WeakPtr< T > && other )

inline

Move constructor.

~WeakPtr()

template<typename T>

~WeakPtr ( )

inline

Member Function Documentation

Expired()

template<typename T>

bool Expired ( ) const

inline

Whether the observed object has been destroyed (or this WeakPtr is null).

Warning

Racy hint only: the object may be destroyed by another thread immediately after this returns false. Never gate a dereference on it; use Lock() instead.

Lock()

template<typename T>

RefPtr< T > Lock ( ) const

inline

Atomically take a strong reference to the observed object.

Returns

Returns a RefPtr keeping the object alive, or a null RefPtr if the object has been destroyed (or this WeakPtr is null).

operator=() [1/4]

template<typename T>

template<typename U>

WeakPtr & operator= ( const RefPtr< U > & strong )

inline

operator=() [2/4]

template<typename T>

WeakPtr & operator= ( const WeakPtr< T > & other )

inline

operator=() [3/4]

template<typename T>

WeakPtr & operator= ( std::nullptr_t )

inline

operator=() [4/4]

template<typename T>

WeakPtr & operator= ( WeakPtr< T > && other )

inline

Reset()

template<typename T>

void Reset ( )

inline

Stop observing the object and become a null WeakPtr.

swap()

template<typename T>

void swap ( WeakPtr< T > & other )

inline

Exchanges the observed objects of *this and other.

Friends And Related Symbol Documentation

WeakPtr

template<typename T>

template<typename U>

friend class WeakPtr

friend

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The documentation for this class was generated from the following file:

• Ultralight/RefPtr.h