xentara::utils::windows::com::Variant Class Reference

A COM variant object. More...

#include <xentara/utils/windows/com/Variant.hpp>

Classes
class	Setter
	Helper class for calling functions that take an output parameter. More...

Public Types
template<VARTYPE Type>
using	NativeType = typename variantTypes::detail::VariantNativeType< Type >::Type
	Facility to determine the native type for a variant type.

Public Member Functions
	Variant () noexcept
	Default constructor.
internal	Variant (VARIANT &&variant) noexcept
	Constructor that takes ownership of a native variant.
auto	operator= (VARIANT &&variant) noexcept -> Variant &
	Assignment operator that takes ownership of a native variant.
auto	type () const -> VARTYPE
	Returns the variant type.
auto	convert (VARTYPE type) const -> Variant
	Converts the variant to a different type.
template<VARTYPE kType>
auto	get () const -> NativeType< kType >
	Gets the value of the variant.
template<VARTYPE kType>
auto	as () const -> NativeType< kType >
	Converts the value of the variant to a certain type.
auto	setter () noexcept -> Setter
	Gets a setter for use as an output parameter for C functions.

Detailed Description

A COM variant object.

This class wraps a COM VARIANT structure.

Member Typedef Documentation

NativeType

template<VARTYPE Type>

using xentara::utils::windows::com::Variant::NativeType = typename variantTypes::detail::VariantNativeType<Type>::Type

Facility to determine the native type for a variant type.

Constructor & Destructor Documentation

Variant() [1/2]

xentara::utils::windows::com::Variant::Variant ( )

noexcept

Default constructor.

This constructor creates an empty variant

Variant() [2/2]

internal xentara::utils::windows::com::Variant::Variant ( VARIANT &&  variant )

noexcept

Constructor that takes ownership of a native variant.

variant The native variant. The variant is cleared.

Member Function Documentation

as()

template<VARTYPE kType>

auto xentara::utils::windows::com::Variant::as

(

)

const -> NativeType< kType >

Converts the value of the variant to a certain type.

Returns

The value as the given type

Exceptions

std::runtime_error

The value cannet be converted to the specified type

convert()

auto xentara::utils::windows::com::Variant::convert

(

VARTYPE

type

)

const -> Variant

Converts the variant to a different type.

Returns

The value as the given type

Exceptions

std::runtime_error

The variant could not be converted

get()

template<VARTYPE kType>

auto xentara::utils::windows::com::Variant::get

(

)

const -> NativeType< kType >

Gets the value of the variant.

This function does not perform any type conversion. Use as() to get the type using conversion.

Returns

The value

Exceptions

std::runtime_error

The value is not of the specified type

operator=()

auto xentara::utils::windows::com::Variant::operator= ( VARIANT &&  variant ) -> Variant &

noexcept

Assignment operator that takes ownership of a native variant.

variant The native variant. The variant is cleared.

Returns

A reference to this object

setter()

auto xentara::utils::windows::com::Variant::setter ( ) -> Setter

noexcept

Gets a setter for use as an output parameter for C functions.

This function returns a helper object that can be passed to a function that takes a VARIANT * as output parameter, like e.g. IWbemClassObject::Get(). This provides a safe way of creating objects using such a function without running the risk of leaking the created object.

IWbemClassObject::Get() can be called like this, for example:

xentara::utils::windows::com::Variant variant;
object->Get(myPropertyName, 0, variant.setter(), nullptr, nullptr);

type()

auto xentara::utils::windows::com::Variant::type

(

)

const -> VARTYPE

Returns the variant type.

Returns

The variant type. The type will be one of the VT_* type codes, possibly ORed together with VT_ARRAY. The value VT_BYREF is masked out.