donner::OptionalRef< T > Class Template Reference

A class that simulates an optional reference to a constant object of type T. More...

#include "donner/base/OptionalRef.h"

Public Types
using	Type = const std::remove_cvref_t<T>
	Type of the referenced object.

Public Member Functions
constexpr	OptionalRef () noexcept=default
	Constructs an empty OptionalRef.
	OptionalRef (std::nullopt_t nullopt) noexcept
	Constructs an empty OptionalRef from a std::nullopt.
constexpr	OptionalRef (const T &ref) noexcept
	Constructs an OptionalRef that contains a reference to the given object.
	~OptionalRef () noexcept=default
	Destructor.
constexpr	OptionalRef (const OptionalRef &other) noexcept=default
	Copy constructor.
constexpr	OptionalRef (OptionalRef &&other) noexcept=default
	Move constructor.
OptionalRef &	operator= (const OptionalRef &other) noexcept=default
	Copy assignment operator.
OptionalRef &	operator= (OptionalRef &&other) noexcept=default
	Move assignment operator.
OptionalRef &	operator= (const T &ref) noexcept
	Assigns a reference to the given object.
void	reset () noexcept
	Resets the OptionalRef to be empty.
constexpr	operator bool () const noexcept
	Returns true if the OptionalRef contains a reference.
constexpr bool	hasValue () const noexcept
	Returns true if the OptionalRef contains a reference.
constexpr const T &	value () const
	Returns a const reference to the referenced object.
constexpr const T &	operator* () const
	Returns a const reference to the referenced object.
constexpr const Type *	operator-> () const noexcept
	Returns a pointer to the referenced object.
constexpr	operator std::optional< T > () const
	Implicit conversion to a std::optional<T>.

Friends
constexpr friend bool	operator== (const OptionalRef &lhs, const OptionalRef &rhs)
	Equality operator to another OptionalRef.
constexpr friend bool	operator== (const OptionalRef &lhs, std::nullopt_t)
	Equality operator to a std::nullopt.
constexpr friend bool	operator== (const OptionalRef &lhs, const T &rhs)
	Equality operator for a set value.
std::ostream &	operator<< (std::ostream &os, const OptionalRef &opt)
	Stream output operator.

Detailed Description

template<typename T>
class donner::OptionalRef< T >

A class that simulates an optional reference to a constant object of type T.

This class behaves similarly to std::optional<const T&>, which is proposed by the upcoming P2988 std::optional<T&> proposal, providing a way to store an optional reference to a constant object. Since std::optional cannot be used with reference types, OptionalRef provides a workaround.

Note

The referenced object must outlive the OptionalRef. It is the responsibility of the user to ensure that the reference remains valid.

Template Parameters

T	The type of the object to reference.

Constructor & Destructor Documentation

OptionalRef() [1/4]

template<typename T >

donner::OptionalRef< T >::OptionalRef ( std::nullopt_t nullopt )

inlinenoexcept

Constructs an empty OptionalRef from a std::nullopt.

Parameters

nullopt

Accepts std::nullopt to construct an empty OptionalRef.

OptionalRef() [2/4]

template<typename T >

constexpr donner::OptionalRef< T >::OptionalRef ( const T & ref )

inlineconstexprnoexcept

Constructs an OptionalRef that contains a reference to the given object.

Parameters

ref	The object to reference.

OptionalRef() [3/4]

template<typename T >

constexpr donner::OptionalRef< T >::OptionalRef ( const OptionalRef< T > & other )

constexprdefaultnoexcept

Copy constructor.

Parameters

other

The other OptionalRef to copy from.

OptionalRef() [4/4]

template<typename T >

constexpr donner::OptionalRef< T >::OptionalRef ( OptionalRef< T > && other )

constexprdefaultnoexcept

Move constructor.

Parameters

other

The other OptionalRef to move from.

Member Function Documentation

hasValue()

template<typename T >

constexpr bool donner::OptionalRef< T >::hasValue ( ) const

inlineconstexprnoexcept

Returns true if the OptionalRef contains a reference.

Returns

true if the OptionalRef is not empty.

operator bool()

template<typename T >

constexpr donner::OptionalRef< T >::operator bool ( ) const

inlineexplicitconstexprnoexcept

Returns true if the OptionalRef contains a reference.

Returns

true if the OptionalRef is not empty.

operator*()

template<typename T >

constexpr const T & donner::OptionalRef< T >::operator* ( ) const

inlineconstexpr

Returns a const reference to the referenced object.

Returns

Const reference to the object.

Note

Asserts that the OptionalRef is not empty.

operator->()

template<typename T >

constexpr const Type * donner::OptionalRef< T >::operator-> ( ) const

inlineconstexprnoexcept

Returns a pointer to the referenced object.

Returns

Pointer to the object.

Note

Asserts that the OptionalRef is not empty.

operator=() [1/3]

template<typename T >

OptionalRef & donner::OptionalRef< T >::operator= ( const OptionalRef< T > & other )

defaultnoexcept

Copy assignment operator.

Parameters

other

The other OptionalRef to copy from.

Returns

Reference to this OptionalRef.

operator=() [2/3]

template<typename T >

OptionalRef & donner::OptionalRef< T >::operator= ( const T & ref )

inlinenoexcept

Assigns a reference to the given object.

Parameters

ref	The object to reference.

Returns

Reference to this OptionalRef.

operator=() [3/3]

template<typename T >

OptionalRef & donner::OptionalRef< T >::operator= ( OptionalRef< T > && other )

defaultnoexcept

Move assignment operator.

Parameters

other

The other OptionalRef to move from.

Returns

Reference to this OptionalRef.

value()

template<typename T >

constexpr const T & donner::OptionalRef< T >::value ( ) const

inlineconstexpr

Returns a const reference to the referenced object.

Returns

Const reference to the object.

Note

Asserts that the OptionalRef is not empty.

Friends And Related Symbol Documentation

operator<<

template<typename T >

std::ostream & operator<< ( std::ostream & os, const OptionalRef< T > & opt )

friend

Stream output operator.

Parameters

os	Output stream.
opt	The OptionalRef to output.

Returns

Reference to the output stream.

Note

Outputs the referenced object if not empty, otherwise outputs "nullopt".

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

• donner/base/OptionalRef.h