SharedResourcePointer< SharedObjectType > Class Template Reference

A smart-pointer that automatically creates and manages the lifetime of a shared static instance of a class. More...

Public Member Functions
	SharedResourcePointer ()=default
	Creates an instance of the shared object.
	SharedResourcePointer (const SharedResourcePointer &)=default
	Copy constructor.
	SharedResourcePointer (SharedResourcePointer &&) noexcept=default
	Move constructor.
	~SharedResourcePointer ()=default
	Destructor.
	operator SharedObjectType * () const noexcept
	Returns a pointer to the shared object.
SharedObjectType &	get () const noexcept
	Returns a reference to the shared object.
SharedObjectType &	getObject () const noexcept
	Returns a reference to the shared object.
SharedObjectType *	operator-> () const noexcept
	Returns a pointer to the shared object.
SharedObjectType &	operator* () const noexcept
	Returns a reference to the shared object.

Static Public Member Functions
static std::optional< SharedResourcePointer >	getSharedObjectWithoutCreating ()
	Returns the SharedResourcePointer if one already exists, or a null optional otherwise.

Detailed Description

template<typename SharedObjectType>
class SharedResourcePointer< SharedObjectType >

A smart-pointer that automatically creates and manages the lifetime of a shared static instance of a class.

The SharedObjectType template type indicates the class to use for the shared object - the only requirements on this class are that it must have a public default constructor and destructor.

The SharedResourcePointer offers a pattern that differs from using a singleton or static instance of an object, because it uses reference-counting to make sure that the underlying shared object is automatically created/destroyed according to the number of SharedResourcePointer objects that exist. When the last one is deleted, the underlying object is also immediately destroyed. This allows you to use scoping to manage the lifetime of a shared resource.

Note: The construction/deletion of the shared object must not involve any code that makes recursive calls to a SharedResourcePointer, or you'll cause a deadlock.

Example:

// An example of a class that contains the shared data you want to use.
struct MySharedData
{
    // There's no need to ever create an instance of this class directly yourself,
    // but it does need a public constructor that does the initialisation.
    MySharedData()
    {
        sharedStuff = generateHeavyweightStuff();
    }
 
    Array<SomeKindOfData> sharedStuff;
};
 
struct DataUserClass
{
    DataUserClass()
    {
        // Multiple instances of the DataUserClass will all have the same
        // shared common instance of MySharedData referenced by their sharedData
        // member variables.
        useSharedStuff (sharedData->sharedStuff);
    }
 
    // By keeping this pointer as a member variable, the shared resource
    // is guaranteed to be available for as long as the DataUserClass object.
    SharedResourcePointer<MySharedData> sharedData;
};

Constructor & Destructor Documentation

SharedResourcePointer() [1/3]

template<typename SharedObjectType>

SharedResourcePointer< SharedObjectType >::SharedResourcePointer ( )

default

Creates an instance of the shared object.

If other SharedResourcePointer objects for this type already exist, then this one will simply point to the same shared object that they are already using. Otherwise, if this is the first SharedResourcePointer to be created, then a shared object will be created automatically.

Referenced by getSharedObjectWithoutCreating(), SharedResourcePointer(), SharedResourcePointer(), and ~SharedResourcePointer().

SharedResourcePointer() [2/3]

template<typename SharedObjectType>

SharedResourcePointer< SharedObjectType >::SharedResourcePointer ( const SharedResourcePointer< SharedObjectType > & )

default

Copy constructor.

References SharedResourcePointer().

SharedResourcePointer() [3/3]

template<typename SharedObjectType>

SharedResourcePointer< SharedObjectType >::SharedResourcePointer ( SharedResourcePointer< SharedObjectType > && )

defaultnoexcept

Move constructor.

References SharedResourcePointer().

~SharedResourcePointer()

template<typename SharedObjectType>

SharedResourcePointer< SharedObjectType >::~SharedResourcePointer ( )

default

Destructor.

If no other SharedResourcePointer objects exist, this will also delete the shared object to which it refers.

References SharedResourcePointer().

Member Function Documentation

operator SharedObjectType *()

template<typename SharedObjectType>

SharedResourcePointer< SharedObjectType >::operator SharedObjectType * ( ) const

noexcept

Returns a pointer to the shared object.

get()

template<typename SharedObjectType>

SharedObjectType & SharedResourcePointer< SharedObjectType >::get ( ) const

noexcept

Returns a reference to the shared object.

getObject()

template<typename SharedObjectType>

SharedObjectType & SharedResourcePointer< SharedObjectType >::getObject ( ) const

noexcept

Returns a reference to the shared object.

operator->()

template<typename SharedObjectType>

SharedObjectType * SharedResourcePointer< SharedObjectType >::operator-> ( ) const

noexcept

Returns a pointer to the shared object.

operator*()

template<typename SharedObjectType>

SharedObjectType & SharedResourcePointer< SharedObjectType >::operator* ( ) const

noexcept

Returns a reference to the shared object.

getSharedObjectWithoutCreating()

template<typename SharedObjectType>

static std::optional< SharedResourcePointer > SharedResourcePointer< SharedObjectType >::getSharedObjectWithoutCreating ( )

static

Returns the SharedResourcePointer if one already exists, or a null optional otherwise.

References SharedResourcePointer().