elm::Option< T > Class Template Reference

#include <elm/util/Option.h>

Public Member Functions
	Option (void)
	Option (const OptionalNone &none)
	Option (T value)
	Option (const Option< T > &opt)
bool	isOne (void) const
bool	isNone (void) const
T	value (void) const
	operator bool (void) const
T	operator* (void) const
	operator T (void) const
Option< T > &	operator= (const Option< T > &opt)
Option< T > &	operator= (T value)

Detailed Description

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

This class is very handly 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

template<class T>

elm::Option< T >::Option

(

void

)

Build an empty optional value recording there is no value.

template<class T>

elm::Option< T >::Option

(

const OptionalNone &

none

)

For nternal use only.

template<class T>

elm::Option< T >::Option

(

T

value

)

References elm::asis_t< T >::put().

template<class T>

elm::Option< T >::Option

(

const Option< T > &

opt

)

Build an optional value by copying an existing one.

Parameters

opt	Optional value to clone.

Member Function Documentation

template<class T>

bool elm::Option< T >::isNone

(

void

)

const

Test if no value is available.

Returns

True if no value is available, false else.

template<class T>

bool elm::Option< T >::isOne

(

void

)

const

Test if a value is available.

Returns

True if a value is available, false else.

Referenced by elm::Option< T >::operator bool().

template<class T>

elm::Option< T >::operator bool

(

void

)

const

Returns

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

References elm::Option< T >::isOne().

template<class T>

elm::Option< T >::operator T

(

void

)

const

Convert to the stored value.

References elm::Option< T >::value().

template<class T>

T elm::Option< T >::operator*

(

void

)

const

Returns

The stored value.

References elm::Option< T >::value().

template<class T>

Option< T > & elm::Option< T >::operator=

(

const Option< T > &

opt

)

Provides assignment support.

Parameters

opt	Optional value to assign.

Returns

Current object.

template<class T>

Option<T>& elm::Option< T >::operator=

(

T

value

)

References elm::asis_t< T >::put().

template<class T>

T elm::Option< T >::value

(

void

)

const

Get the value.

Returns

The stored value.

Warning

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

References elm::asis_t< T >::get().

Referenced by elm::Option< T >::operator T(), and elm::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