Variant Data Types

The Variant classes deal with strongly typed variant data. More...

Classes
class	Glib::DBusObjectPathString
	String class for D-Bus object paths in Glib::Variant. More...
class	Glib::DBusSignatureString
	String class for D-Bus signatures in Glib::Variant. More...
class	Glib::DBusHandle
	Class for D-Bus handles in Glib::Variant. More...
class	Glib::VariantBase
	This is the base class for all Variant types. More...
class	Glib::VariantStringBase
	Base class from which string variant classes derive. More...
class	Glib::VariantContainerBase
	The base class for multiple-item Variants, such as Variants containing tuples or arrays, and also for maybe-typed (that is, nullable) Variant types. More...
class	Glib::Variant< T >
	Template class used for the specialization of the Variant<> classes. More...
class	Glib::Variant< VariantBase >
	Specialization of Variant containing a VariantBase. More...
class	Glib::Variant< Variant< T > >
	Specialization of Variant containing a Variant<T>. More...
class	Glib::Variant< Glib::ustring >
	Specialization of Variant containing a Glib::ustring, for variants of type string, object path, or signature. More...
class	Glib::Variant< Glib::DBusObjectPathString >
	Specialization of Variant containing a Glib::DBusObjectPathString, for variants of type object path. More...
class	Glib::Variant< Glib::DBusSignatureString >
	Specialization of Variant containing a Glib::DBusSignatureString, for variants of type signature. More...
class	Glib::Variant< std::string >
	Specialization of Variant containing a std::string, for variants of type bytestring, string, object path, or signature. More...
class	Glib::Variant< std::vector< T > >
	Specialization of Variant containing an array of items. More...
class	Glib::Variant< std::vector< Glib::ustring > >
	Specialization of Variant containing an array of UTF-8 capable strings. More...
class	Glib::Variant< std::vector< Glib::DBusObjectPathString > >
	Specialization of Variant containing an array of D-Bus object paths. More...
class	Glib::Variant< std::vector< std::string > >
	Specialization of Variant containing an array of non-UTF-8 strings (byte string arrays). More...
class	Glib::Variant< std::map< K, V > >
	Specialization of Variant containing a dictionary (a map of (key, value) elements). More...
class	Glib::Variant< std::tuple< Types... > >
	Specialization of Variant containing a tuple. More...
class	Glib::VariantType
	VariantType - The VariantBase type system. More...
class	Glib::Variant< bool >
	Specialization of Glib::Variant containing a bool type. More...
class	Glib::Variant< unsigned char >
	Specialization of Glib::Variant containing a unsigned char type. More...
class	Glib::Variant< gint16 >
	Specialization of Glib::Variant containing a gint16 type. More...
class	Glib::Variant< guint16 >
	Specialization of Glib::Variant containing a guint16 type. More...
class	Glib::Variant< gint32 >
	Specialization of Glib::Variant containing a gint32 type. More...
class	Glib::Variant< guint32 >
	Specialization of Glib::Variant containing a guint32 type. More...
class	Glib::Variant< long >
	Specialization of Glib::Variant containing a long type. More...
class	Glib::Variant< unsigned long >
	Specialization of Glib::Variant containing a unsigned long type. More...
class	Glib::Variant< long long >
	Specialization of Glib::Variant containing a long long type. More...
class	Glib::Variant< unsigned long long >
	Specialization of Glib::Variant containing a unsigned long long type. More...
class	Glib::Variant< DBusHandle >
	Specialization of Glib::Variant containing a DBusHandle type. More...
class	Glib::Variant< double >
	Specialization of Glib::Variant containing a double type. More...

Functions
template<typename T >
Variant< T >	create_variant (const T &data)
	Creates a Glib::Variant instance.

Detailed Description

The Variant classes deal with strongly typed variant data.

A Variant stores a value along with information about the type of that value. The range of possible values is determined by the type. The type system used is VariantType.

See the VariantBase class and its derived types, such as VariantContainerBase, and the Variant<> template type.

Variant instances always have a type and a value (which are given at construction time). The type and value of a Variant can never change other than by the Variant itself being destroyed. A Variant cannot contain a pointer.

Variant is heavily optimised for dealing with data in serialised form. It works particularly well with data located in memory-mapped files. It can perform nearly all deserialisation operations in a small constant time, usually touching only a single memory page. Serialised Variant data can also be sent over the network.

Variant is largely compatible with D-Bus. Almost all types of Variant instances can be sent over D-Bus. See VariantType for exceptions.

There is a Python-inspired text language for describing Variant values. Variant includes a printer for this language and a parser with type inferencing.

Function Documentation

create_variant()

template <typename T >

Variant< T > create_variant ( const T &  data )

related

Creates a Glib::Variant instance.

std::vector<int> int_vector = { 1, 2, 3, 4, 5, 6, 7, 8 };
auto int_vector_variant = Glib::create_variant(int_vector);

is an alternative to

std::vector<int> int_vector = { 1, 2, 3, 4, 5, 6, 7, 8 };
auto int_vector_variant = Glib::Variant<std::vector<int>>::create(int_vector);

Glib::create_variant() can usually deduce the type of the Glib::Variant from the type of the argument.

There is no Glib::Variant<const char*> specialization.

auto variant1 = Glib::create_variant("Hello, World!"); // Error
auto variant2 = Glib::create_variant<Glib::ustring>("Hello, World!"); // OK
auto variant3 = Glib::create_variant(Glib::ustring("Hello, World!")); // OK
auto variant4 = Glib::Variant<Glib::ustring>::create("Hello, World!"); // OK

Since glibmm 2.78: