optional< T > Class Template Reference

This class is a replacement for C++17 std::optional. More...

#include <cvb/shims/optional.hpp>

Public Member Functions
	optional () noexcept
	Default ctor not storing a value.
	optional (nullopt_t) noexcept
	Ctor for explicitly not storing a value.
template<class... ARGS>
	optional (in_place_t, ARGS &&... args)
	In-place constructs a new T object. More...
template<class U , typename std::enable_if< std::is_assignable< T &, U >::value, int >::type = 0>
	optional (U &&value)
	Ctor from an object assignable to T. More...
template<class U , typename std::enable_if< std::is_assignable< T &, U >::value, int >::type = 0>
optional &	operator= (U &&value)
	Assignment operator for an object assignable to T. More...
template<typename std::enable_if< std::is_copy_constructible< T >::value, int >::type = 0>
	optional (const optional &rhs)
	Copy ctor. More...
template<typename std::enable_if< std::is_copy_assignable< T >::value, int >::type = 0>
optional &	operator= (const optional &rhs)
	Copy operator. More...
template<typename std::enable_if< std::is_move_constructible< T >::value, int >::type = 0>
	optional (optional &&rhs)
	Move ctor. More...
template<typename std::enable_if< std::is_move_assignable< T >::value, int >::type = 0>
optional &	operator= (optional &&rhs)
	Move operator. More...
const T *	operator-> () const noexcept
	Gets the reference to the stored object. More...
T *	operator-> () noexcept
	Gets the reference to the stored object. More...
const T &	operator* () const noexcept
	Gets the reference to the stored object. More...
T &	operator* () noexcept
	Gets the reference to the stored object. More...
	operator bool () const noexcept
	Gets whether this optional contains a value. More...
template<class... ARGS>
T &	emplace (ARGS &&... args)
	Constructs a new T in-place. More...
bool	has_value () const noexcept
	Gets whether this optional contains a value. More...
void	reset ()
	Destroys any contained value.
void	swap (optional &other)
	Swaps this object with the other object. More...
const T &	value () const
	Gets the contained value. More...
T &	value ()
	Gets the contained value. More...
template<class U , typename std::enable_if< std::is_assignable< T &, U >::value, int >::type = 0>
T	value_or (U &&default_value) const
	Gets the contained value if has_value() is true; default_value otherwise. More...

Detailed Description

template<class T>
class Cvb::Shims::optional< T >

This class is a replacement for C++17 std::optional.

Constructor & Destructor Documentation

optional() [1/4]

optional ( in_place_t  , ARGS &&...  args  )

inline

In-place constructs a new T object.

Template Parameters

ARGS	Type list of all arguments to be forwarded to T.

Parameters

[in]

args

Arguments that are forwarded to the ctor of

optional() [2/4]

optional ( U &&  value )

inline

Ctor from an object assignable to T.

Template Parameters

U	Type assignable to T.

Parameters

[in]

value

Value to store.

optional() [3/4]

optional ( const optional< T > &  rhs )

inline

Copy ctor.

Parameters

[in]

rhs

Object to copy.

optional() [4/4]

optional ( optional< T > &&  rhs )

inline

Move ctor.

Parameters

[in]

rhs

Object to copy.

Member Function Documentation

emplace()

T & emplace ( ARGS &&...  args )

inline

Constructs a new T in-place.

If a this object has_value() is true, the old value is destroyed via its destructor.

Template Parameters

ARGS	Type list of all arguments to be forwarded to T.

Parameters

[in]

args

Command line arguments forwarded to the ctor of T.

Returns

Reference to the newly created object.

has_value()

bool has_value ( ) const

inlinenoexcept

Gets whether this optional contains a value.

Returns

true if this object contains a value;

operator bool()

operator bool ( ) const

inlineexplicitnoexcept

Gets whether this optional contains a value.

Returns

true if this object contains a value;

operator*() [1/2]

const T & operator* ( ) const

inlinenoexcept

Gets the reference to the stored object.

Precondition

has_value() == true

Returns

Reference to the contained value.

operator*() [2/2]

T & operator* ( )

inlinenoexcept

Gets the reference to the stored object.

Precondition

has_value() == true

Returns

Reference to the contained value.

operator->() [1/2]

const T * operator-> ( ) const

inlinenoexcept

Gets the reference to the stored object.

Precondition

has_value() == true

Returns

Reference to the contained value.

operator->() [2/2]

T * operator-> ( )

inlinenoexcept

Gets the reference to the stored object.

Precondition

has_value() == true

Returns

Reference to the contained value.

operator=() [1/3]

optional & operator= ( const optional< T > &  rhs )

inline

Copy operator.

Parameters

[in]

rhs

Object to copy.

Returns

Reference to this object.

operator=() [2/3]

optional & operator= ( optional< T > &&  rhs )

inline

Move operator.

Parameters

[in]

rhs

Object to copy.

Returns

Reference to this object.

operator=() [3/3]

optional & operator= ( U &&  value )

inline

Assignment operator for an object assignable to T.

Template Parameters

U	Type assignable to T.

Parameters

[in]

value

Value to store.

Returns

Reference to this object.

swap()

void swap ( optional< T > &  other )

inline

Swaps this object with the other object.

The contents of this and the other are swapped.

Parameters

[in]

other

Optional to swap value with.

value() [1/2]

T & value ( )

inline

Gets the contained value.

Returns

Reference to the contained value.

Exceptions

bad_optional_access

thrown if has_value() is false.

value() [2/2]

const T & value ( ) const

inline

Gets the contained value.

Returns

Reference to the contained value.

Exceptions

bad_optional_access

thrown if has_value() is false.

value_or()

T value_or ( U &&  default_value ) const

inline

Gets the contained value if has_value() is true; default_value otherwise.

Returns

Either the contained value or the default_value.