Type used for fields with default values of nothing. More...

Inheritance diagram for bond::maybe< T, typename boost::enable_if< detail::has_allocator< T > >::type >:

Public Types
using	allocator_type = typename T::allocator_type
	The type of the allocator in use. More...

using	value_type = T
	The type of the value that may be inside the maybe. More...

Public Member Functions
	maybe (const maybe &)=default
	Copy a maybe. More...

	maybe (maybe &&)=default
	Move a maybe. More...

	maybe (const maybe &that, const allocator_type &alloc)
	Allocator-extended copy constructor. Uses alloc as the new allocator, makes a copy of `that`. More...

	maybe (maybe &&that, const allocator_type &alloc)
	Allocator-extended move constructor. Uses alloc as the new allocator, makes moved from `that`. More...

	maybe (const allocator_type &alloc)
	Construct a maybe that holds nothing, but remember the allocator so that it can be used to construct a T if needed. More...

	maybe (const T &value)
	Create a maybe that holds a copy of `value`. More...

	maybe (T &&value)
	Create a maybe that holds a value by moving from `value`. More...

maybe &	operator= (const T &value)
	Assign by copying `value`. More...

maybe &	operator= (T &&value)
	Move-assign from `value`. More...

T &	set_value ()
	Set to non-empty, if needed. More...

void	swap (maybe &that)
	Swap this object with `that`. More...

allocator_type	get_allocator () const BOND_NOEXCEPT
	Get the allocator that this maybe uses. More...

bool	is_nothing () const BOND_NOEXCEPT
	Check if this object contains nothing. More...

	operator bool () const BOND_NOEXCEPT
	Check if this object contains a value. More...

void	set_nothing () BOND_NOEXCEPT
	Set to nothing. More...

template<typename... Args>
T &	emplace (Args &&... args)
	Construct a value in place. More...

T &	value ()
	Get a reference to the value. More...

const T &	value () const
	Get a constant reference to the value. More...

T &	value (const std::nothrow_t &) BOND_NOEXCEPT
	Get a reference to the value. More...

const T &	value (const std::nothrow_t &) const BOND_NOEXCEPT
	Get a constant reference to the value. More...

Friends
bool	operator== (const maybe &lhs, const maybe &rhs)
	Compares two maybes for value equality. More...

bool	operator!= (const maybe &lhs, const maybe &rhs)
	Compares two maybes for value inequality. More...

Detailed Description

template<typename T>
class bond::maybe< T, typename boost::enable_if< detail::has_allocator< T > >::type >

Type used for fields with default values of nothing.

This specialization is used for instances of T with allocators.

See the User's Manual for more details about default values of nothing.

See also

For details of maybe's comparison operators, see

Member Typedef Documentation

◆ allocator_type

template<typename T >

using bond::maybe< T, typename boost::enable_if< detail::has_allocator< T > >::type >::allocator_type = typename T::allocator_type

The type of the allocator in use.

◆ value_type

template<typename T >

using bond::detail::maybe_common< T >::value_type = T

inherited

The type of the value that may be inside the maybe.

Constructor & Destructor Documentation

◆ maybe() [1/7]

template<typename T >

bond::maybe< T, typename boost::enable_if< detail::has_allocator< T > >::type >::maybe ( const maybe< T, typename boost::enable_if< detail::has_allocator< T > >::type > & )

default

Copy a maybe.

◆ maybe() [2/7]

template<typename T >

bond::maybe< T, typename boost::enable_if< detail::has_allocator< T > >::type >::maybe ( maybe< T, typename boost::enable_if< detail::has_allocator< T > >::type > && )

default

Move a maybe.

Note: Unlike std::optional, a moved-from maybe holds nothing (compared to a moved-from T).

◆ maybe() [3/7]

template<typename T >

bond::maybe< T, typename boost::enable_if< detail::has_allocator< T > >::type >::maybe	(	const maybe< T, typename boost::enable_if< detail::has_allocator< T > >::type > &	that,
		const allocator_type &	alloc
	)

Allocator-extended copy constructor. Uses alloc as the new allocator, makes a copy of that.

◆ maybe() [4/7]

template<typename T >

bond::maybe< T, typename boost::enable_if< detail::has_allocator< T > >::type >::maybe	(	maybe< T, typename boost::enable_if< detail::has_allocator< T > >::type > &&	that,
		const allocator_type &	alloc
	)

Allocator-extended move constructor. Uses alloc as the new allocator, makes moved from that.

Note: Unlike std::optional, a moved-from maybe holds nothing (compared to a moved-from T).

◆ maybe() [5/7]

template<typename T >

bond::maybe< T, typename boost::enable_if< detail::has_allocator< T > >::type >::maybe ( const allocator_type & alloc )

explicit

Construct a maybe that holds nothing, but remember the allocator so that it can be used to construct a T if needed.

Since: 8.0.0

◆ maybe() [6/7]

template<typename T >

bond::maybe< T, typename boost::enable_if< detail::has_allocator< T > >::type >::maybe ( const T & value )

explicit

Create a maybe that holds a copy of value.

◆ maybe() [7/7]

template<typename T >

bond::maybe< T, typename boost::enable_if< detail::has_allocator< T > >::type >::maybe ( T && value )

Create a maybe that holds a value by moving from value.

Since: 8.0.0

Member Function Documentation

◆ emplace()

template<typename T >

template<typename... Args>

T & bond::detail::maybe_common< T >::emplace ( Args &&... args )

inherited

Construct a value in place.

Since: 8.0.0

◆ get_allocator()

template<typename T >

allocator_type bond::maybe< T, typename boost::enable_if< detail::has_allocator< T > >::type >::get_allocator ( ) const

Get the allocator that this maybe uses.

Since: 8.0.0

◆ is_nothing()

template<typename T >

bool bond::detail::maybe_common< T >::is_nothing ( ) const

inherited

Check if this object contains nothing.

Returns: true if this holds nothing; otherwise false.

◆ operator bool()

template<typename T >

bond::detail::maybe_common< T >::operator bool ( ) const

explicitinherited

Check if this object contains a value.

Returns: true if this object holds a value; otherwise false.

Since: 8.0.0

◆ operator=() [1/2]

template<typename T >

maybe & bond::maybe< T, typename boost::enable_if< detail::has_allocator< T > >::type >::operator= ( const T & value )

Assign by copying value.

◆ operator=() [2/2]

template<typename T >

maybe & bond::maybe< T, typename boost::enable_if< detail::has_allocator< T > >::type >::operator= ( T && value )

Move-assign from value.

Since: 8.0.0

◆ set_nothing()

template<typename T >

void bond::detail::maybe_common< T >::set_nothing ( )

inherited

Set to nothing.

◆ set_value()

template<typename T >

T & bond::maybe< T, typename boost::enable_if< detail::has_allocator< T > >::type >::set_value ( )

Set to non-empty, if needed.

If this object contains nothing, construct an instance of T, passing it the saved allocator; otherwise, preserve the existing value.

Returns: A reference to the value.

◆ swap()

template<typename T >

void bond::maybe< T, typename boost::enable_if< detail::has_allocator< T > >::type >::swap ( maybe< T, typename boost::enable_if< detail::has_allocator< T > >::type > & that )

Swap this object with that.

◆ value() [1/4]

template<typename T >

T & bond::detail::maybe_common< T >::value ( )

inherited

Get a reference to the value.

Exceptions

CoreException if the object contains nothing

◆ value() [2/4]

template<typename T >

const T & bond::detail::maybe_common< T >::value ( ) const

inherited

Get a constant reference to the value.

Exceptions

CoreException if the object contains nothing

◆ value() [3/4]

template<typename T >

T & bond::detail::maybe_common< T >::value ( const std::nothrow_t & )

inherited

Get a reference to the value.

Will never throw, but has undefined behavior if the object contains nothing.

Since: 8.0.0

◆ value() [4/4]

template<typename T >

const T & bond::detail::maybe_common< T >::value ( const std::nothrow_t & ) const

inherited

Get a constant reference to the value.

Will never throw, but has undefined behavior if the object contains nothing.

Since: 8.0.0

Friends And Related Function Documentation

◆ operator!=

template<typename T >

bool operator!=	(	const maybe< T, typename boost::enable_if< detail::has_allocator< T > >::type > &	lhs,
		const maybe< T, typename boost::enable_if< detail::has_allocator< T > >::type > &	rhs
	)

friend

Compares two maybes for value inequality.

See operator==(const maybe_common&,const maybe_common&) for details about how maybes holding nothing are handled.

◆ operator==

template<typename T >

bool operator==	(	const maybe< T, typename boost::enable_if< detail::has_allocator< T > >::type > &	lhs,
		const maybe< T, typename boost::enable_if< detail::has_allocator< T > >::type > &	rhs
	)

friend

Compares two maybes for value equality.

Returns: true if both maybes hold nothing; returns false if one maybe holds nothing and the other holds a values; otherwise, calls operator== with the two values.

Public Types

Public Member Functions

Friends

Detailed Description

Member Typedef Documentation

◆ allocator_type

◆ value_type

Constructor & Destructor Documentation

◆ maybe() [1/7]

◆ maybe() [2/7]

◆ maybe() [3/7]

◆ maybe() [4/7]

◆ maybe() [5/7]

◆ maybe() [6/7]

◆ maybe() [7/7]

Member Function Documentation

◆ emplace()

◆ get_allocator()

◆ is_nothing()

◆ operator bool()

◆ operator=() [1/2]

◆ operator=() [2/2]

◆ set_nothing()

◆ set_value()

◆ swap()

◆ value() [1/4]

◆ value() [2/4]

◆ value() [3/4]

◆ value() [4/4]

Friends And Related Function Documentation

◆ operator!=

◆ operator==