Option< T > Class Template Reference

#include <elm/util/Option.h>

Public Member Functions
	Option ()
	Option (const OptionalNone &none)
	Option (t::in< T > value)
	Option (const Option< T > &opt)
bool	some () const
bool	none () const
t::ret< T >	value () const
t::ret< T >	operator* () const
template<class F >
const Option< T > &	if_one (const F &f) const
template<class F >
const Option< T > &	if_else (const F &f) const
Option< T > &	operator= (const Option< T > &opt)
Option< T > &	operator= (t::in< T > value)
bool	equals (const OptionalNone &_) const
bool	equals (const Option< T > &opt) const
bool	operator== (const OptionalNone &_) const
bool	operator!= (const OptionalNone &_) const
bool	operator== (const Option< T > &o) const
bool	operator!= (const Option< T > &o) const
	operator bool (void) const
	operator t::ret< T > () const
bool	isOne () const
bool	isNone () const

Detailed Description

template<class T>
class elm::Option< T >

This class is very handy to manage parameters or return value that may be optional. This class records there is no value or there is a value and the instance of the value.

To build it, you may be easier to use the special value elm::none or the special function elm::some() instead of the class constructors.

   if(cannot_compute)
       return none;
else
       return some(result);

Please consider the conversion operator allowing to test of the availability of a value by putting it straight-forward in a condition or accessing the value by putting the optional value in place where the value may be used.

Option<int> val = f();
if(val)
    x += val;

Parameters

T	Type of the stored value.

Constructor & Destructor Documentation

Option() [1/4]

Option ( )

inline

Option() [2/4]

Option ( const OptionalNone &  none )

inline

@fn Option::Option();

Build an empty optional value recording there is no value.

For nternal use only.

Option() [3/4]

Option ( t::in< T >  value )

inline

Build an optional value containing the given one.

Parameters

value

Value to store.

Option() [4/4]

Option ( const Option< T > &  opt )

inline

Build an optional value by copying an existing one.

Parameters

opt	Optional value to clone.

Member Function Documentation

equals() [1/2]

bool equals ( const Option< T > &  opt ) const

inline

References Option< T >::none(), and Option< T >::some().

equals() [2/2]

bool equals ( const OptionalNone &  _ ) const

inline

References Option< T >::none().

Referenced by Option< T >::operator!=(), and Option< T >::operator==().

if_else()

const Option<T>& if_else ( const F &  f ) const

inline

if_one()

const Option<T>& if_one ( const F &  f ) const

inline

isNone()

bool isNone ( ) const

inline

Test if no value is available.

Returns

True if no value is available, false else.

Referenced by StrictMapDelegate< C >::get().

isOne()

bool isOne ( ) const

inline

Test if a value is available.

Returns

True if a value is available, false else.

none()

bool none ( ) const

inline

Referenced by Option< T >::equals(), Option< T >::operator!=(), and Option< T >::operator==().

operator bool()

operator bool ( void  ) const

inline

Returns

Evaluates to true if a value is available, false else.

References Option< T >::some().

operator t::ret< T >()

operator t::ret< T > ( ) const

inline

Convert to the stored value.

Deprecated:

References Option< T >::value().

operator!=() [1/2]

bool operator!= ( const Option< T > &  o ) const

inline

References Option< T >::equals().

operator!=() [2/2]

bool operator!= ( const OptionalNone &  _ ) const

inline

References Option< T >::none().

operator*()

t::ret< T > operator* ( ) const

inline

Returns

The stored value.

References Option< T >::value().

operator=() [1/2]

Option< T > & operator= ( const Option< T > &  opt )

inline

Provides assignment support.

Parameters

opt	Optional value to assign.

Returns

Current object.

operator=() [2/2]

Option<T>& operator= ( t::in< T >  value )

inline

References type_info< T >::put().

operator==() [1/2]

bool operator== ( const Option< T > &  o ) const

inline

References Option< T >::equals().

operator==() [2/2]

bool operator== ( const OptionalNone &  _ ) const

inline

References Option< T >::none().

some()

bool some ( ) const

inline

Referenced by Option< T >::equals(), Option< T >::operator bool(), and AbstractAttribute::parse().

value()

t::ret< T > value ( ) const

inline

Get the value.

Returns

The stored value.

Warning

It is an error to call this method if no value is available.

Referenced by Option< T >::operator t::ret< T >(), and Option< T >::operator*().

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

• include/elm/util/Option.h
• src/util_Option.cpp