dds::core::optional< T > Class Template Reference

<<value-type>> Represents an object that may not contain a valid value More...

#include <dds/core/Optional.hpp>

Public Member Functions
	optional () OMG_NOEXCEPT
	Create an unset optional object.
	optional (const T &value)
	Create an optional object with a copy of a value.
	optional (T &&value)
	<<C++11>> Create an optional object moving a value
	optional (bool condition, const T &value)
	Create an optional member conditionally set or unset.
	optional (bool condition, T &&value)
	<<C++11>> Creates an optional member conditionally set or unset by moving a value.
	~optional ()
	Destroys the underlying object if it exists.
void	set (const T &value)
	Assigns a copy of an object.
void	set (T &&value)
	<<C++11>> Assigns an object by moving it
bool	is_set () const OMG_NOEXCEPT
	Checks if this optional instance contains a valid object.
bool	has_value () const OMG_NOEXCEPT
	Checks if this optional instance contains a valid object.
	operator bool () const OMG_NOEXCEPT
	Returns has_value()
void	reset ()
	Destroys the underlying object and leaves this optional with an invalid (unset) value.
const T &	value () const
	Retrieves the underlying object if it exists.
T &	value ()
	Retrieves the underlying object if it exists.
const T &	get () const
	Retrieves the underlying object if it exists.
T &	get ()
	Retrieves the underlying object if it exists.
const T *	get_ptr () const
	Returns &get() if the object is initialized or NULL otherwise.
T *	get_ptr ()
	Returns &get() if the object is initialized or NULL otherwise.
const T &	operator* () const
T &	operator* ()
const T *	operator-> () const
T *	operator-> ()
optional< T > &	operator= (const optional< T > &other)
	Assignment operator.
optional< T > &	operator= (optional< T > &&other) OMG_NOEXCEPT
	<<C++11>> Move-assignment operator
optional< T > &	operator= (const T &value)
	Assign a (valid) value.
optional< T > &	operator= (T &&value)
	Assign a (valid) value by moving an object.

Friends
void	swap (optional< T > &left, optional< T > &right) OMG_NOEXCEPT
	Swaps the underlying objects.

Related Functions
(Note that these are not member functions.)
template<typename T >
bool	operator== (const optional< T > &a, const optional< T > &b)
	Compares two optional values.
template<typename T >
bool	operator!= (const optional< T > &a, const optional< T > &b)
	Compares two optional values.
template<typename T >
bool	operator== (const optional< T > &optional_value, const T &value)
	Compares an optional member and a value of the underlying type.
template<typename T >
bool	operator== (const T &value, const optional< T > &optional_value)
	Compares an optional member and a value of the underlying type.
template<typename T >
bool	operator!= (const optional< T > &optional_value, const T &value)
	Compares an optional member and a value of the underlying type.
template<typename T >
bool	operator!= (const T &value, const optional< T > &optional_value)
	Compares an optional member and a value of the underlying type.
template<typename T >
std::ostream &	operator<< (std::ostream &out, const optional< T > &optional)
	Applies operator<< to *optional or to the string "NULL" if !optional.has_value().

Detailed Description

template<typename T>
class dds::core::optional< T >

<<value-type>> Represents an object that may not contain a valid value

Template Parameters

T	The type of the actual object this optional<T> wraps

Members of an IDL type marked with the @optional tag map to this C++ type.

When an optional value has a valid value has_value() returns true and operator* returns a reference to the actual object of type T. Otherwise has_value() returns false and operator* throws dds::core::PreconditionNotMetError. To assing a value you can use the assignment operator.

An optional object has full value-type semantics; copying an optional value copies the underlying object if it exists.

This type's API is similar to that of std::optional.

See Also

Working with IDL types

Constructor & Destructor Documentation

template<typename T>

dds::core::optional< T >::optional ( )

inline

Create an unset optional object.

Postcondition

!has_value()

template<typename T>

dds::core::optional< T >::optional ( const T &  value )

inline

Create an optional object with a copy of a value.

Postcondition

has_value() && *(*this) == value

template<typename T>

dds::core::optional< T >::optional ( T &&  value )

inline

<<C++11>> Create an optional object moving a value

Postcondition

has_value()

template<typename T>

dds::core::optional< T >::optional ( bool  condition, const T &  value  )

inline

Create an optional member conditionally set or unset.

Parameters

condition	If true creates an optional member with value otherwise it creates an unset optional member
value	The value to set if condition is true

Postcondition

has_value() == condition

template<typename T>

dds::core::optional< T >::optional ( bool  condition, T &&  value  )

inline

<<C++11>> Creates an optional member conditionally set or unset by moving a value.

Moves the value rather than copying it.

See Also

optional(bool, const T&)

template<typename T>

dds::core::optional< T >::~optional ( )

inline

Destroys the underlying object if it exists.

Member Function Documentation

template<typename T>

void dds::core::optional< T >::set ( const T &  value )

inline

Assigns a copy of an object.

[DEPRECATED] Use operator= instead.

template<typename T>

void dds::core::optional< T >::set ( T &&  value )

inline

<<C++11>> Assigns an object by moving it

[DEPRECATED] Use operator= instead.

template<typename T>

bool dds::core::optional< T >::is_set ( ) const

inline

Checks if this optional instance contains a valid object.

[DEPRECATED] Use has_value()

template<typename T>

bool dds::core::optional< T >::has_value ( ) const

inline

Checks if this optional instance contains a valid object.

If my_optional->has_value(), then *my_optional returns a valid object

template<typename T>

dds::core::optional< T >::operator bool ( ) const

inline

Returns has_value()

template<typename T>

void dds::core::optional< T >::reset ( )

inline

Destroys the underlying object and leaves this optional with an invalid (unset) value.

Postcondition

!has_value()

template<typename T>

const T& dds::core::optional< T >::value ( ) const

inline

Retrieves the underlying object if it exists.

This operation, unlike operator* throws an exception if the underlying object doesn't exist.

Exceptions

dds::core::PreconditionNotMetError

if !has_value().

template<typename T>

T& dds::core::optional< T >::value ( )

inline

Retrieves the underlying object if it exists.

This operation, unlike operator* throws an exception if the underlying object doesn't exist.

Exceptions

dds::core::PreconditionNotMetError

if !has_value().

template<typename T>

const T& dds::core::optional< T >::get ( ) const

inline

Retrieves the underlying object if it exists.

[DEPRECATED] Use value() or operator*

Exceptions

dds::core::PreconditionNotMetError

if !has_value().

template<typename T>

T& dds::core::optional< T >::get ( )

inline

Retrieves the underlying object if it exists.

[DEPRECATED] Use value() or operator*

Exceptions

dds::core::PreconditionNotMetError

if !has_value().

template<typename T>

const T* dds::core::optional< T >::get_ptr ( ) const

inline

Returns &get() if the object is initialized or NULL otherwise.

[DEPRECATED]

template<typename T>

T* dds::core::optional< T >::get_ptr ( )

inline

Returns &get() if the object is initialized or NULL otherwise.

[DEPRECATED]

template<typename T>

const T& dds::core::optional< T >::operator* ( ) const

inline

Get the value, without checking if it exists

Precondition

has_value(), otherwise this operation has undefined behavior. See value().

template<typename T>

T& dds::core::optional< T >::operator* ( )

inline

Get the value, without checking if it exists

Precondition

has_value(), otherwise this operation has undefined behavior. See value().

template<typename T>

const T* dds::core::optional< T >::operator-> ( ) const

inline

Get the value.

Exceptions

dds::core::PreconditionNotMetError

if !has_value()

template<typename T>

T* dds::core::optional< T >::operator-> ( )

inline

Get the value.

Exceptions

dds::core::PreconditionNotMetError

if !has_value()

template<typename T>

optional<T>& dds::core::optional< T >::operator= ( const optional< T > &  other )

inline

Assignment operator.

Copies *other if it exists.

template<typename T>

optional<T>& dds::core::optional< T >::operator= ( optional< T > &&  other )

inline

<<C++11>> Move-assignment operator

Moves *other if it exists.

template<typename T>

optional<T>& dds::core::optional< T >::operator= ( const T &  value )

inline

Assign a (valid) value.

Parameters

value

The value to assign to this optional member

Postcondition

*(*this) == value

template<typename T>

optional<T>& dds::core::optional< T >::operator= ( T &&  value )

inline

Assign a (valid) value by moving an object.

Parameters

value

The value to move into this optional member

Postcondition

has_value()

Friends And Related Function Documentation

template<typename T>

void swap ( optional< T > &  left, optional< T > &  right  )

friend

Swaps the underlying objects.

This operation is always O(1).

template<typename T >

bool operator== ( const optional< T > &  a, const optional< T > &  b  )

related

Compares two optional values.

Returns

true if both are unset or both are set and *a == *b.

template<typename T >

bool operator!= ( const optional< T > &  a, const optional< T > &  b  )

related

Compares two optional values.

Returns

false if both are unset or both are set and *a == *b.

template<typename T >

bool operator== ( const optional< T > &  optional_value, const T &  value  )

related

Compares an optional member and a value of the underlying type.

Returns

Return true if optional_value is set and *optional_value == value

template<typename T >

bool operator== ( const T &  value, const optional< T > &  optional_value  )

related

Compares an optional member and a value of the underlying type.

Returns

Return true if optional_value is set and *optional_value == value

template<typename T >

bool operator!= ( const optional< T > &  optional_value, const T &  value  )

related

Compares an optional member and a value of the underlying type.

Returns

Return false if optional_value is set and *optional_value == value

template<typename T >

bool operator!= ( const T &  value, const optional< T > &  optional_value  )

related

Compares an optional member and a value of the underlying type.

Returns

Return false if optional_value is set and *optional_value == value

template<typename T >

std::ostream & operator<< ( std::ostream &  out, const optional< T > &  optional  )

related

Applies operator<< to *optional or to the string "NULL" if !optional.has_value().