optional< T > Class Template Reference

A template class to manage an optional contained value. More...

#include <optional.hpp>

Public Types
using	value_type = T
	The type of the value to manage initialization state for.

Public Member Functions
constexpr inline	optional () noexcept(noexcept(T()))=default
	Default constructor that constructs an optional object without a contained value.
constexpr inline	optional (std::nullptr_t) noexcept(noexcept(T()))
	Constructs an optional object that does not contain a value.
constexpr inline	optional (const value_type &val) noexcept(noexcept(T(val)))
	Copy constructor that constructs an optional object with a contained value, initializing it with val.
constexpr inline	optional (value_type &&val) noexcept
	Move constructor that constructs an optional object with a contained value, initializing it with val.
constexpr inline	optional (const optional< T > &opt) noexcept
	Copy constructor that constructs an optional object with a contained value, copying it from opt.
constexpr inline optional &	operator= (std::nullptr_t) noexcept
	Assignment operator that clears the contained value of the optional object.
constexpr inline optional &	operator= (value_type &&val) noexcept
	Move assignment operator that sets the contained value of the optional object to val.
constexpr inline optional &	operator= (const optional< T > &opt) noexcept
	Assigns the value and the state of existence from another optional object.
constexpr inline value_type *	operator-> () noexcept
	Pointer access to the contained value.
constexpr inline const value_type *	operator-> () const noexcept
	Constant pointer access to the contained value.
constexpr inline value_type &	operator* () noexcept
	Reference access to the contained value.
constexpr inline const value_type &	operator* () const noexcept
	Constant reference access to the contained value.
constexpr inline	operator bool () const noexcept
	Checks existence of the contained value.
constexpr inline bool	has_value () const noexcept
	Checks existence of the contained value.
constexpr inline value_type &	value () &noexcept
	Reference access to the contained value.
constexpr inline const value_type &	value () const &noexcept
	Constant reference access to the contained value.
constexpr inline value_type &&	value () &&noexcept
	Move access to the contained value.
constexpr inline const value_type &&	value () const &&noexcept
	Constant move access to the contained value.

Detailed Description

template<typename T>
class ipaddress::optional< T >

A template class to manage an optional contained value.

The optional class template is often used to represent the outcome of a function that might not succeed. An optional<T> can either hold a value or be empty at any moment. When it does hold a value, that value is stored within the optional object itself, meaning there’s no need for separate dynamic memory allocation. If you check an optional<T> in a boolean context, such as in an if-statement, it will evaluate to true if there’s a value present, and false otherwise.

Template Parameters

T	The type of the value to manage initialization state for.

Constructor & Destructor Documentation

optional() [1/3]

template<typename T >

constexpr inline optional ( const value_type & val )

inlinenoexcept

Copy constructor that constructs an optional object with a contained value, initializing it with val.

Parameters

[in]

val

The value to copy into the optional object.

optional() [2/3]

template<typename T >

constexpr inline optional ( value_type && val )

inlinenoexcept

Move constructor that constructs an optional object with a contained value, initializing it with val.

Parameters

[in,out]

val

The value to move into the optional object.

optional() [3/3]

template<typename T >

constexpr inline optional ( const optional< T > & opt )

inlinenoexcept

Copy constructor that constructs an optional object with a contained value, copying it from opt.

Parameters

[in]

opt

The optional object to copy the value from.

Member Function Documentation

operator=() [1/3]

template<typename T >

constexpr inline optional & operator= ( std::nullptr_t )

inlinenoexcept

Assignment operator that clears the contained value of the optional object.

Returns

A reference to the optional object.

operator=() [2/3]

template<typename T >

constexpr inline optional & operator= ( value_type && val )

inlinenoexcept

Move assignment operator that sets the contained value of the optional object to val.

Parameters

[in,out]

val

The value to move into the optional object.

Returns

A reference to the optional object.

operator=() [3/3]

template<typename T >

constexpr inline optional & operator= ( const optional< T > & opt )

inlinenoexcept

Assigns the value and the state of existence from another optional object.

Parameters

[in]

opt

The optional object to copy from.

Returns

A reference to *this.

operator->() [1/2]

template<typename T >

constexpr inline value_type * operator-> ( )

inlinenoexcept

Pointer access to the contained value.

Provides pointer access to the contained value. It is undefined behavior if the optional object does not contain a value.

Returns

A pointer to the contained value.

operator->() [2/2]

template<typename T >

constexpr inline const value_type * operator-> ( ) const

inlinenoexcept

Constant pointer access to the contained value.

Provides constant pointer access to the contained value. It is undefined behavior if the optional object does not contain a value.

Returns

A constant pointer to the contained value.

operator*() [1/2]

template<typename T >

constexpr inline value_type & operator* ( )

inlinenoexcept

Reference access to the contained value.

Provides reference access to the contained value. It is undefined behavior if the optional object does not contain a value.

Returns

A reference to the contained value.

operator*() [2/2]

template<typename T >

constexpr inline const value_type & operator* ( ) const

inlinenoexcept

Constant reference access to the contained value.

Provides constant reference access to the contained value. It is undefined behavior if the optional object does not contain a value.

Returns

A constant reference to the contained value.

operator bool()

template<typename T >

constexpr inline operator bool ( ) const

inlineexplicitnoexcept

Checks existence of the contained value.

Determines whether the optional object contains a value.

Returns

true if a value is contained, otherwise false.

has_value()

template<typename T >

constexpr inline bool has_value ( ) const

inlinenoexcept

Checks existence of the contained value.

Determines whether the optional object contains a value.

Returns

true if a value is contained, otherwise false.

value() [1/4]

template<typename T >

constexpr inline value_type & value ( ) &

inlinenoexcept

Reference access to the contained value.

Provides reference access to the contained value. It is undefined behavior if the optional object does not contain a value.

Returns

A reference to the contained value.

value() [2/4]

template<typename T >

constexpr inline const value_type & value ( ) const &

inlinenoexcept

Constant reference access to the contained value.

Provides constant reference access to the contained value. It is undefined behavior if the optional object does not contain a value.

Returns

A constant reference to the contained value.

value() [3/4]

template<typename T >

constexpr inline value_type && value ( ) &&

inlinenoexcept

Move access to the contained value.

Moves the contained value. It is undefined behavior if the optional object does not contain a value.

Returns

The contained value, moved.

value() [4/4]

template<typename T >

constexpr inline const value_type && value ( ) const &&

inlinenoexcept

Constant move access to the contained value.

Moves the contained value, maintaining constness. It is undefined behavior if the optional object does not contain a value.

Returns

The contained value, moved, as a constant.

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

• include/ipaddress/optional.hpp