Package org.gnome.gobject

Class WeakRef<T extends GObject>

java.lang.Object

io.github.jwharm.javagi.base.ProxyInstance

org.gnome.gobject.WeakRef<T>

All Implemented Interfaces:

Proxy

@Generated("io.github.jwharm.JavaGI")
public class WeakRef<T extends GObject>
extends ProxyInstance

A structure containing a weak reference to a GObject.

A GWeakRef can either be empty (i.e. point to null), or point to an object for as long as at least one "strong" reference to that object exists. Before the object's GObjectClass.dispose method is called, every GWeakRef associated with becomes empty (i.e. points to null).

Like GValue, GWeakRef can be statically allocated, stack- or heap-allocated, or embedded in larger structures.

Unlike g_object_weak_ref() and g_object_add_weak_pointer(), this weak reference is thread-safe: converting a weak pointer to a reference is atomic with respect to invalidation of weak pointers to destroyed objects.

If the object's GObjectClass.dispose method results in additional references to the object being held (‘re-referencing’), any GWeakRefs taken before it was disposed will continue to point to null. Any GWeakRefs taken during disposal and after re-referencing, or after disposal has returned due to the re-referencing, will continue to point to the object until its refcount goes back to zero, at which point they too will be invalidated.

It is invalid to take a GWeakRef on an object during GObjectClass.dispose without first having or creating a strong reference to the object.

Constructor Summary

Constructors

Constructor	Description
WeakRef()	Allocate a new WeakRef.
WeakRef(Arena arena)	Allocate a new WeakRef.
WeakRef(MemorySegment address)	Create a WeakRef proxy instance for the provided memory address.

Method Summary

Modifier and Type	Method	Description
void	clear()	Frees resources associated with a non-statically-allocated GWeakRef.
T	get()	If this WeakRef is not empty, atomically acquire a strong reference to the object it points to, and return that reference.
static MemoryLayout	getMemoryLayout()	The memory layout of the native struct.
void	init(T object)	Initialise a non-statically-allocated GWeakRef.
MemorySegment	readP()	Read the value of the field p.
void	set(T object)	Change the object to which this WeakRef points, or set it to null.
void	writeP(MemorySegment p)	Write a value in the field p.

Methods inherited from class io.github.jwharm.javagi.base.ProxyInstance

equals, handle, hashCode

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Constructor Details

WeakRef

public WeakRef(MemorySegment address)

Create a WeakRef proxy instance for the provided memory address.

Parameters:

address - the memory address of the native object

WeakRef

public WeakRef(Arena arena)

Allocate a new WeakRef.

Parameters:

arena - to control the memory allocation scope

WeakRef

public WeakRef()

Allocate a new WeakRef. The memory is allocated with Arena.ofAuto().

Method Details

getMemoryLayout

public static MemoryLayout getMemoryLayout()

The memory layout of the native struct.

Returns:

the memory layout

readP

public MemorySegment readP()

Read the value of the field p.

Returns:

The value of the field p

writeP

public void writeP(MemorySegment p)

Write a value in the field p.

Parameters:

p - The new value for the field p

clear

public void clear()

Frees resources associated with a non-statically-allocated GWeakRef. After this call, the GWeakRef is left in an undefined state.

You should only call this on a GWeakRef that previously had g_weak_ref_init() called on it.

get

public T get()

If this WeakRef is not empty, atomically acquire a strong reference to the object it points to, and return that reference.

This function is needed because of the potential race between taking the pointer value and g_object_ref() on it, if the object was losing its last reference at the same time in a different thread.

The caller should release the resulting reference in the usual way, by using g_object_unref().

Returns:

the object pointed to by this WeakRef, or null if it was empty

init

public void init(@Nullable
 T object)

Initialise a non-statically-allocated GWeakRef.

This function also calls g_weak_ref_set() with object on the freshly-initialised weak reference.

This function should always be matched with a call to g_weak_ref_clear(). It is not necessary to use this function for a GWeakRef in static storage because it will already be properly initialised. Just use g_weak_ref_set() directly.

Parameters:

object - a GObject or null

set

public void set(@Nullable
 T object)

Change the object to which this WeakRef points, or set it to null.

You must own a strong reference on object while calling this function.

Parameters:

object - a GObject or null