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 WeakReference< ObjectType, ReferenceCountingType >:

Collaboration diagram for 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
typedef ReferenceCountedObjectPtr< SharedPointer >	SharedRef

Public Member Functions
	WeakReference () noexcept
	Creates a null SafePointer. More...
	WeakReference (ObjectType *const object)
	Creates a WeakReference that points at the given object. More...
	WeakReference (const WeakReference &other) noexcept
	Creates a copy of another WeakReference. 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 *const object) const noexcept
ObjectType *	operator-> () noexcept
	Returns the object that this pointer refers to, or null if the object no longer exists. More...
const 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 *const newObject)
	Copies another pointer to this one. More...
WeakReference &	operator= (WeakReference &&other) noexcept
	Move assignment operator. More...
bool	operator== (ObjectType *const 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 SharedPointer *	getRef (ObjectType *const o)

Private Attributes
SharedRef	holder

Detailed Description

template<class ObjectType, class ReferenceCountingType = ReferenceCountedObject>
class 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.

E.g.

class MyObject
{
public:
    MyObject()
    {
        // If you're planning on using your WeakReferences in a multi-threaded situation, you may choose
        // to create a WeakReference to the object here in the constructor, which will pre-initialise the
        // embedded object, avoiding an (extremely unlikely) race condition that could occur if multiple
        // threads overlap while creating the first WeakReference to it.
    }

    ~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>;
};

// Here's an example of using a pointer..

MyObject* n = new MyObject();
WeakReference<MyObject> myObjectRef = n;

MyObject* pointer1 = myObjectRef;  // returns a valid pointer to 'n'
delete n;
MyObject* pointer2 = myObjectRef;  // returns a null pointer

See also

WeakReference::Master

Member Typedef Documentation

SharedRef

template<class ObjectType, class ReferenceCountingType = ReferenceCountedObject>

typedef ReferenceCountedObjectPtr<SharedPointer> WeakReference< ObjectType, ReferenceCountingType >::SharedRef

Constructor & Destructor Documentation

WeakReference() [1/4]

template<class ObjectType, class ReferenceCountingType = ReferenceCountedObject>

WeakReference< ObjectType, ReferenceCountingType >::WeakReference ( )

inlinenoexcept

Creates a null SafePointer.

WeakReference() [2/4]

template<class ObjectType, class ReferenceCountingType = ReferenceCountedObject>

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

inline

Creates a WeakReference that points at the given object.

WeakReference() [3/4]

template<class ObjectType, class ReferenceCountingType = ReferenceCountedObject>

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>

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

inlinenoexcept

Move constructor.

Member Function Documentation

get()

template<class ObjectType, class ReferenceCountingType = ReferenceCountedObject>

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

inlinenoexcept

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

getRef()

template<class ObjectType, class ReferenceCountingType = ReferenceCountedObject>

static SharedPointer* WeakReference< ObjectType, ReferenceCountingType >::getRef ( ObjectType *const  o )

inlinestaticprivate

Referenced by WeakReference< InterprocessConnection >::operator=().

operator ObjectType *()

template<class ObjectType, class ReferenceCountingType = ReferenceCountedObject>

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

inlinenoexcept

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

operator!=()

template<class ObjectType, class ReferenceCountingType = ReferenceCountedObject>

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

inlinenoexcept

operator->() [1/2]

template<class ObjectType, class ReferenceCountingType = ReferenceCountedObject>

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

inlinenoexcept

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

operator->() [2/2]

template<class ObjectType, class ReferenceCountingType = ReferenceCountedObject>

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

inline

Copies another pointer to this one.

operator=() [3/3]

template<class ObjectType, class ReferenceCountingType = ReferenceCountedObject>

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

inlinenoexcept

Move assignment operator.

operator==()

template<class ObjectType, class ReferenceCountingType = ReferenceCountedObject>

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

inlinenoexcept

wasObjectDeleted()

template<class ObjectType, class ReferenceCountingType = ReferenceCountedObject>

bool 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 WeakReference< ObjectType, ReferenceCountingType >::holder

private

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

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

• juce_WeakReference.h