gmx::Variant Class Reference

#include <gromacs/utility/variant.h>

Description

Represents a dynamically typed value of an arbitrary type.

To create a variant, either initialize it as empty, or with the create() method (or the equivalent constructor, if the type parameter can be deduced and is clear to the reader from the context).

To query the type of the contents in the variant, use isEmpty(), type(), and isType().

To access the value, you need to know the type as a compile-time constant (e.g., through branching based on isType()), and then use cast() or tryCast().

Methods in this class do not throw unless otherwise indicated.

This provides essentially the same functionality as boost::any.

Public Member Functions
	Variant ()
	Creates an empty variant value.
template<typename T >
	Variant (const T &value)
	Creates a variant that holds the given value. More...
template<typename T >
	Variant (T &&value)
	Creates a variant that holds the given value. More...
	Variant (const Variant &other)
	Creates a deep copy of a variant. More...
	Variant (Variant &&other) noexcept
	Move-constructs a variant.
Variant &	operator= (const Variant &other)
	Assigns the variant. More...
Variant &	operator= (Variant &&other) noexcept
	Move-assigns the variant.
bool	isEmpty () const
	Whether any value is stored.
std::type_index	type () const
	Returns the dynamic type of the value that is currently stored.
template<typename T >
bool	isType () const
	Returns whether the type stored matches the template parameter.
template<typename T >
const T *	tryCast () const
	Tries to get the value as the given type. More...
template<typename T >
const T &	cast () const
	Gets the value when the type is known. More...
template<typename T >
T *	tryCastRef ()
	Tries to get the value as the given type as a non-const pointer. More...
template<typename T >
T &	castRef ()
	Gets the value when the type is known as a modifiable reference. More...

Static Public Member Functions
template<typename T >
static Variant	create (const T &value)
	Creates a variant that holds the given value. More...
template<typename T >
static Variant	create (T &&value)
	Creates a variant that holds the given value. More...

Constructor & Destructor Documentation

template<typename T >

gmx::Variant::Variant ( const T &  value )

inlineexplicit

Creates a variant that holds the given value.

Exceptions

std::bad_alloc

if out of memory.

template<typename T >

gmx::Variant::Variant ( T &&  value )

inlineexplicit

Creates a variant that holds the given value.

Exceptions

std::bad_alloc

if out of memory.

gmx::Variant::Variant ( const Variant &  other )

inline

Creates a deep copy of a variant.

Exceptions

std::bad_alloc

if out of memory.

Member Function Documentation

template<typename T >

const T& gmx::Variant::cast ( ) const

inline

Gets the value when the type is known.

Template Parameters

T	Type to get (which must match what the variant stores).

Asserts if the variant is empty or does not contain the requested type.

template<typename T >

T& gmx::Variant::castRef ( )

inline

Gets the value when the type is known as a modifiable reference.

Template Parameters

T	Type to get (which must match what the variant stores).

Asserts if the variant is empty or does not contain the requested type.

template<typename T >

static Variant gmx::Variant::create ( const T &  value )

inlinestatic

Creates a variant that holds the given value.

Exceptions

std::bad_alloc

if out of memory.

This method allows explicitly specifying the template argument, contrary to the templated constructor.

template<typename T >

static Variant gmx::Variant::create ( T &&  value )

inlinestatic

Creates a variant that holds the given value.

Exceptions

std::bad_alloc

if out of memory.

In addition to allowing specifying the template argument, this method avoids copying when move-construction is possible.

Variant& gmx::Variant::operator= ( const Variant &  other )

inline

Assigns the variant.

Exceptions

std::bad_alloc

if out of memory.

template<typename T >

const T* gmx::Variant::tryCast ( ) const

inline

Tries to get the value as the given type.

Template Parameters

T	Type to get.

Returns

Pointer to the value, or nullptr if the type does not match the stored value.

template<typename T >

T* gmx::Variant::tryCastRef ( )

inline

Tries to get the value as the given type as a non-const pointer.

Template Parameters

T	Type to get.

Returns

Pointer to the value, or nullptr if the type does not match the stored value.

This method allows modifying the value in-place, which is useful with more complicated data structures.

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

• src/gromacs/utility/variant.h