juce::WeakReference< ObjectType, ReferenceCountingType > Class Template Reference

This class acts as a pointer which will automatically become null if the object to which it points is deleted. More...

#include <juce_WeakReference.h>

Inheritance diagram for juce::WeakReference< ObjectType, ReferenceCountingType >:

Collaboration diagram for juce::WeakReference< ObjectType, ReferenceCountingType >:

Classes
class	Master
	This class is embedded inside an object to which you want to attach WeakReference pointers. More...
class	SharedPointer
	This class is used internally by the WeakReference class - don't use it directly in your code! More...

Public Types
using	SharedRef = ReferenceCountedObjectPtr< SharedPointer >

Public Member Functions
	WeakReference ()=default
	Creates a null WeakReference. More...
	WeakReference (const WeakReference &other) noexcept
	Creates a copy of another WeakReference. More...
	WeakReference (ObjectType *object)
	Creates a WeakReference that points at the given object. More...
	WeakReference (WeakReference &&other) noexcept
	Move constructor. More...
ObjectType *	get () const noexcept
	Returns the object that this pointer refers to, or null if the object no longer exists. More...
	operator ObjectType * () const noexcept
	Returns the object that this pointer refers to, or null if the object no longer exists. More...
bool	operator!= (ObjectType *object) const noexcept
ObjectType *	operator-> () const noexcept
	Returns the object that this pointer refers to, or null if the object no longer exists. More...
WeakReference &	operator= (const WeakReference &other)
	Copies another pointer to this one. More...
WeakReference &	operator= (ObjectType *newObject)
	Copies another pointer to this one. More...
WeakReference &	operator= (WeakReference &&other) noexcept
	Move assignment operator. More...
bool	operator== (ObjectType *object) const noexcept
bool	wasObjectDeleted () const noexcept
	This returns true if this reference has been pointing at an object, but that object has since been deleted. More...

Static Private Member Functions
static SharedRef	getRef (ObjectType *o)

Private Attributes
SharedRef	holder

Detailed Description

template<class ObjectType, class ReferenceCountingType = ReferenceCountedObject>
class juce::WeakReference< ObjectType, ReferenceCountingType >

This class acts as a pointer which will automatically become null if the object to which it points is deleted.

To accomplish this, the source object needs to cooperate by performing a couple of simple tasks. It must embed a WeakReference::Master object, which stores a shared pointer object, and must clear this master pointer in its destructor.

Note that WeakReference is not designed to be thread-safe, so if you're accessing it from different threads, you'll need to do your own locking around all uses of the pointer and the object it refers to.

E.g.

class MyObject
{
public:
    MyObject() {}
 
    ~MyObject()
    {
        // This will zero all the references - you need to call this in your destructor.
        masterReference.clear();
    }
 
private:
    // You need to embed a variable of this type, with the name "masterReference" inside your object. If the
    // variable is not public, you should make your class a friend of WeakReference<MyObject> so that the
    // WeakReference class can access it.
    WeakReference<MyObject>::Master masterReference;
    friend class WeakReference<MyObject>;
};
 
OR: just use the handy JUCE_DECLARE_WEAK_REFERENCEABLE macro to do all this for you.
 
// Here's an example of using a pointer..
 
auto* n = new MyObject();
WeakReference<MyObject> myObjectRef = n;
 
auto pointer1 = myObjectRef.get();  // returns a valid pointer to 'n'
delete n;
auto pointer2 = myObjectRef.get();  // now returns nullptr

See also

WeakReference::Master

@tags{Core}

Member Typedef Documentation

SharedRef

template<class ObjectType , class ReferenceCountingType = ReferenceCountedObject>

using juce::WeakReference< ObjectType, ReferenceCountingType >::SharedRef = ReferenceCountedObjectPtr<SharedPointer>

Constructor & Destructor Documentation

WeakReference() [1/4]

template<class ObjectType , class ReferenceCountingType = ReferenceCountedObject>

juce::WeakReference< ObjectType, ReferenceCountingType >::WeakReference ( )

inlinedefault

Creates a null WeakReference.

WeakReference() [2/4]

template<class ObjectType , class ReferenceCountingType = ReferenceCountedObject>

juce::WeakReference< ObjectType, ReferenceCountingType >::WeakReference ( ObjectType *  object )

inline

Creates a WeakReference that points at the given object.

WeakReference() [3/4]

template<class ObjectType , class ReferenceCountingType = ReferenceCountedObject>

juce::WeakReference< ObjectType, ReferenceCountingType >::WeakReference ( const WeakReference< ObjectType, ReferenceCountingType > &  other )

inlinenoexcept

Creates a copy of another WeakReference.

WeakReference() [4/4]

template<class ObjectType , class ReferenceCountingType = ReferenceCountedObject>

juce::WeakReference< ObjectType, ReferenceCountingType >::WeakReference ( WeakReference< ObjectType, ReferenceCountingType > &&  other )

inlinenoexcept

Move constructor.

Member Function Documentation

get()

template<class ObjectType , class ReferenceCountingType = ReferenceCountedObject>

ObjectType* juce::WeakReference< ObjectType, ReferenceCountingType >::get ( ) const

inlinenoexcept

Returns the object that this pointer refers to, or null if the object no longer exists.

Referenced by juce::WeakReference< ObjectType, ReferenceCountingType >::operator ObjectType *(), juce::WeakReference< juce::Component >::operator!=(), juce::WeakReference< juce::Component >::operator->(), and juce::WeakReference< juce::Component >::operator==().

getRef()

template<class ObjectType , class ReferenceCountingType = ReferenceCountedObject>

static SharedRef juce::WeakReference< ObjectType, ReferenceCountingType >::getRef ( ObjectType *  o )

inlinestaticprivate

Referenced by juce::WeakReference< juce::Component >::operator=().

operator ObjectType *()

template<class ObjectType , class ReferenceCountingType = ReferenceCountedObject>

juce::WeakReference< ObjectType, ReferenceCountingType >::operator ObjectType * ( ) const

inlinenoexcept

Returns the object that this pointer refers to, or null if the object no longer exists.

References juce::WeakReference< ObjectType, ReferenceCountingType >::get().

operator!=()

template<class ObjectType , class ReferenceCountingType = ReferenceCountedObject>

bool juce::WeakReference< ObjectType, ReferenceCountingType >::operator!= ( ObjectType *  object ) const

inlinenoexcept

operator->()

template<class ObjectType , class ReferenceCountingType = ReferenceCountedObject>

ObjectType* juce::WeakReference< ObjectType, ReferenceCountingType >::operator-> ( ) const

inlinenoexcept

Returns the object that this pointer refers to, or null if the object no longer exists.

operator=() [1/3]

template<class ObjectType , class ReferenceCountingType = ReferenceCountedObject>

WeakReference& juce::WeakReference< ObjectType, ReferenceCountingType >::operator= ( const WeakReference< ObjectType, ReferenceCountingType > &  other )

inline

Copies another pointer to this one.

operator=() [2/3]

template<class ObjectType , class ReferenceCountingType = ReferenceCountedObject>

WeakReference& juce::WeakReference< ObjectType, ReferenceCountingType >::operator= ( ObjectType *  newObject )

inline

Copies another pointer to this one.

operator=() [3/3]

template<class ObjectType , class ReferenceCountingType = ReferenceCountedObject>

WeakReference& juce::WeakReference< ObjectType, ReferenceCountingType >::operator= ( WeakReference< ObjectType, ReferenceCountingType > &&  other )

inlinenoexcept

Move assignment operator.

operator==()

template<class ObjectType , class ReferenceCountingType = ReferenceCountedObject>

bool juce::WeakReference< ObjectType, ReferenceCountingType >::operator== ( ObjectType *  object ) const

inlinenoexcept

wasObjectDeleted()

template<class ObjectType , class ReferenceCountingType = ReferenceCountedObject>

bool juce::WeakReference< ObjectType, ReferenceCountingType >::wasObjectDeleted ( ) const

inlinenoexcept

This returns true if this reference has been pointing at an object, but that object has since been deleted.

If this reference was only ever pointing at a null pointer, this will return false. Using operator=() to make this refer to a different object will reset this flag to match the status of the reference from which you're copying.

Member Data Documentation

holder

template<class ObjectType , class ReferenceCountingType = ReferenceCountedObject>

SharedRef juce::WeakReference< ObjectType, ReferenceCountingType >::holder

private

Referenced by juce::WeakReference< juce::Component >::get(), juce::WeakReference< juce::Component >::operator=(), and juce::WeakReference< juce::Component >::wasObjectDeleted().

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

• juce_WeakReference.h