|
glibmm 2.80.0
|
VariantType - The VariantBase type system. More...
#include <glibmm/varianttype.h>
Public Member Functions | |
| VariantType () | |
| Constructs an invalid object. More... | |
| VariantType (GVariantType * castitem, bool make_a_copy=false) | |
| VariantType (const VariantType & src) | |
| VariantType & | operator= (const VariantType & src) |
| VariantType (VariantType && other) noexcept | |
| VariantType & | operator= (VariantType && other) noexcept |
| ~VariantType () noexcept | |
| void | swap (VariantType & other) noexcept |
| GVariantType * | gobj () |
| const GVariantType * | gobj () const |
| GVariantType * | gobj_copy () const |
| Provides access to the underlying C instance. The caller is responsible for freeing it. Use when directly setting fields in structs. More... | |
| VariantType (const GVariantType * castitem) | |
| Copy the C item into a new VariantType instance. More... | |
| VariantType (const std::string & type_string) | |
| Creates a new VariantType corresponding to the type string given by type_string. More... | |
| VariantType & | operator= (const GVariantType * castitem) |
| gsize | get_string_length () const |
| Returns the length of the type string corresponding to the given type. More... | |
| std::string | get_string () const |
| Returns the type string corresponding to the given type. More... | |
| bool | is_definite () const |
| Determines if the given type is definite (ie: not indefinite). More... | |
| bool | is_container () const |
| Determines if the given type is a container type. More... | |
| bool | is_basic () const |
| Determines if the given type is a basic type. More... | |
| bool | is_maybe () const |
| Determines if the given type is a maybe type. More... | |
| bool | is_array () const |
| Determines if the given type is an array type. More... | |
| bool | is_tuple () const |
| Determines if the given type is a tuple type. More... | |
| bool | is_dict_entry () const |
| Determines if the given type is a dictionary entry type. More... | |
| bool | is_variant () const |
| Determines if the given type is the variant type. More... | |
| guint | hash () const |
| Hashes type. More... | |
| bool | equal (const VariantType & other) const |
| Compares *this and other for equality. More... | |
| bool | is_subtype_of (const VariantType & supertype) const |
| Checks if type is a subtype of supertype. More... | |
| VariantType | element () const |
| Determines the element type of an array or maybe type. More... | |
| gsize | n_items () const |
| Determines the number of items contained in a tuple or dictionary entry type. More... | |
| VariantType | key () const |
| Determines the key type of a dictionary entry type. More... | |
| VariantType | value () const |
| Determines the value type of a dictionary entry type. More... | |
| std::vector< VariantType > | get_item_types () const |
| Determines the item types of a tuple or dictionary entry type. More... | |
Static Public Member Functions | |
| static VariantType | create_array (const VariantType &element) |
| Constructs the type corresponding to an array of elements of the type type. More... | |
| static VariantType | create_maybe (const VariantType &element) |
| Constructs the type corresponding to a maybe instance containing type type or Nothing. More... | |
| static VariantType | create_tuple (const std::vector< VariantType > & items) |
| Constructs a new tuple type, from items. More... | |
| static VariantType | create_dict_entry (const VariantType &key, const VariantType &value) |
| Constructs the type corresponding to a dictionary entry with a key of type key and a value of type value. More... | |
Protected Attributes | |
| GVariantType * | gobject_ |
Related Functions | |
(Note that these are not member functions.) | |
| void | swap (VariantType & lhs, VariantType & rhs) noexcept |
| Glib::VariantType | wrap (GVariantType * object, bool take_copy=false) |
| A Glib::wrap() method for this object. More... | |
VariantType - The VariantBase type system.
The VariantBase type system is based, in large part, on the D-Bus type system, with two major changes and some minor lifting of restrictions. The D-Bus specification, therefore, provides a significant amount of information that is useful when working with VariantBase.
The first major change with respect to the D-Bus type system is the introduction of maybe (or "nullable") types. Any type in VariantBase can be converted to a maybe type, in which case, "nothing" (or "null") becomes a valid value. Maybe types have been added by introducing the character "m" to type strings.
The second major change is that the VariantBase type system supports the concept of "indefinite types" – types that are less specific than the normal types found in D-Bus. For example, it is possible to speak of "an array of any type" in VariantBase, where the D-Bus type system would require you to speak of "an array of integers" or "an array of strings". Indefinite types have been added by introducing the characters "*", "?" and "r" to type strings.
Finally, all arbitrary restrictions relating to the complexity of types are lifted along with the restriction that dictionary entries may only appear nested inside of arrays.
Just as in D-Bus, VariantBase types are described with strings ("type strings"). Subject to the differences mentioned above, these strings are of the same form as those found in D-Bus. Note, however: D-Bus always works in terms of messages and therefore individual type strings appear nowhere in its interface. Instead, "signatures" are a concatenation of the strings of the type of each argument in a message. VariantBase deals with single values directly so VariantBase type strings always describe the type of exactly one value. This means that a D-Bus signature string is generally not a valid VariantBase type string – except in the case that it is the signature of a message containing exactly one argument.
An indefinite type is similar in spirit to what may be called an abstract type in other type systems. No value can exist that has an indefinite type as its type, but values can exist that have types that are subtypes of indefinite types. That is to say, VariantBase::get_type() will never return an indefinite type, but calling VariantBase::is_of_type() with an indefinite type may return true. For example, you cannot have a value that represents "an array of no particular type", but you can have an "array of integers" which certainly matches the type of "an array of no
particular type", since "array of integers" is a subtype of "array of no
particular type".
This is similar to how instances of abstract classes may not directly exist in other type systems, but instances of their non-abstract subtypes may. For example, in gtkmm, no object that has the type of Gtk::Widget can exist (since Gtk::Widget is an abstract class), but a Gtk::Window can certainly be instantiated, and you would say that the Gtk::Window is a Gtk::Widget (since Gtk::Window is a subclass of Gtk::Widget).
See the underlying GVariantType documentation for a detailed description of the VariantBase type strings.
| Glib::VariantType::VariantType | ( | ) |
Constructs an invalid object.
E.g. for output arguments to methods. There is not much you can do with the object before it has been assigned a valid value.
|
explicit |
| Glib::VariantType::VariantType | ( | const VariantType & | src | ) |
|
noexcept |
|
noexcept |
|
explicit |
Copy the C item into a new VariantType instance.
|
explicit |
Creates a new VariantType corresponding to the type string given by type_string.
It is a programmer error to call this function with an invalid type string. Use string_is_valid() if you are unsure.
|
static |
Constructs the type corresponding to an array of elements of the type type.
It is appropriate to call g_variant_type_free() on the return value.
| element | A VariantType. |
|
static |
Constructs the type corresponding to a dictionary entry with a key of type key and a value of type value.
It is appropriate to call g_variant_type_free() on the return value.
| key | A basic VariantType. |
| value | A VariantType. |
|
static |
Constructs the type corresponding to a maybe instance containing type type or Nothing.
It is appropriate to call g_variant_type_free() on the return value.
| element | A VariantType. |
|
static |
Constructs a new tuple type, from items.
| items | A vector of VariantTypes, one for each item. |
| VariantType Glib::VariantType::element | ( | ) | const |
Determines the element type of an array or maybe type.
This function may only be used with array or maybe types.
| bool Glib::VariantType::equal | ( | const VariantType & | other | ) | const |
Compares *this and other for equality.
Only returns true if the types are exactly equal. Even if one type is an indefinite type and the other is a subtype of it, false will be returned if they are not exactly equal. If you want to check for subtypes, use is_subtype_of().
| other | The VariantType to compare with. |
true if *this and other are exactly equal.| std::vector< VariantType > Glib::VariantType::get_item_types | ( | ) | const |
Determines the item types of a tuple or dictionary entry type.
This function may only be used with tuple or dictionary entry types, but must not be used with the generic tuple type VARIANT_TYPE_TUPLE.
In the case of a dictionary entry type, returns a vector with 2 elements, the type of the key followed by the value type.
An empty vector is returned in case of this VariantType being VARIANT_TYPE_UNIT.
| std::string Glib::VariantType::get_string | ( | ) | const |
Returns the type string corresponding to the given type.
The result is not nul-terminated; in order to determine its length you must call g_variant_type_get_string_length().
To get a nul-terminated string, see g_variant_type_dup_string().
| gsize Glib::VariantType::get_string_length | ( | ) | const |
Returns the length of the type string corresponding to the given type.
This function must be used to determine the valid extent of the memory region returned by g_variant_type_peek_string().
|
inline |
|
inline |
| GVariantType * Glib::VariantType::gobj_copy | ( | ) | const |
Provides access to the underlying C instance. The caller is responsible for freeing it. Use when directly setting fields in structs.
| guint Glib::VariantType::hash | ( | ) | const |
Hashes type.
The argument type of type is only #gconstpointer to allow use with HashTable without function pointer casting. A valid VariantType must be provided.
| bool Glib::VariantType::is_array | ( | ) | const |
Determines if the given type is an array type.
This is true if the type string for type starts with an 'a'.
This function returns true for any indefinite type for which every definite subtype is an array type – G_VARIANT_TYPE_ARRAY, for example.
true if type is an array type. | bool Glib::VariantType::is_basic | ( | ) | const |
Determines if the given type is a basic type.
Basic types are booleans, bytes, integers, doubles, strings, object paths and signatures.
Only a basic type may be used as the key of a dictionary entry.
This function returns false for all indefinite types except G_VARIANT_TYPE_BASIC.
true if type is a basic type. | bool Glib::VariantType::is_container | ( | ) | const |
Determines if the given type is a container type.
Container types are any array, maybe, tuple, or dictionary entry types plus the variant type.
This function returns true for any indefinite type for which every definite subtype is a container – G_VARIANT_TYPE_ARRAY, for example.
true if type is a container type. | bool Glib::VariantType::is_definite | ( | ) | const |
Determines if the given type is definite (ie: not indefinite).
A type is definite if its type string does not contain any indefinite type characters ('*', '?', or 'r').
A Variant instance may not have an indefinite type, so calling this function on the result of g_variant_get_type() will always result in true being returned. Calling this function on an indefinite type like G_VARIANT_TYPE_ARRAY, however, will result in false being returned.
true if type is definite. | bool Glib::VariantType::is_dict_entry | ( | ) | const |
Determines if the given type is a dictionary entry type.
This is true if the type string for type starts with a '{'.
This function returns true for any indefinite type for which every definite subtype is a dictionary entry type – G_VARIANT_TYPE_DICT_ENTRY, for example.
true if type is a dictionary entry type. | bool Glib::VariantType::is_maybe | ( | ) | const |
Determines if the given type is a maybe type.
This is true if the type string for type starts with an 'm'.
This function returns true for any indefinite type for which every definite subtype is a maybe type – G_VARIANT_TYPE_MAYBE, for example.
true if type is a maybe type. | bool Glib::VariantType::is_subtype_of | ( | const VariantType & | supertype | ) | const |
Checks if type is a subtype of supertype.
This function returns true if type is a subtype of supertype. All types are considered to be subtypes of themselves. Aside from that, only indefinite types can have subtypes.
| supertype | A VariantType. |
true if type is a subtype of supertype. | bool Glib::VariantType::is_tuple | ( | ) | const |
Determines if the given type is a tuple type.
This is true if the type string for type starts with a '(' or if type is G_VARIANT_TYPE_TUPLE.
This function returns true for any indefinite type for which every definite subtype is a tuple type – G_VARIANT_TYPE_TUPLE, for example.
true if type is a tuple type. | bool Glib::VariantType::is_variant | ( | ) | const |
Determines if the given type is the variant type.
true if type is the variant type. | VariantType Glib::VariantType::key | ( | ) | const |
Determines the key type of a dictionary entry type.
This function may only be used with a dictionary entry type. Other than the additional restriction, this call is equivalent to g_variant_type_first().
| gsize Glib::VariantType::n_items | ( | ) | const |
Determines the number of items contained in a tuple or dictionary entry type.
This function may only be used with tuple or dictionary entry types, but must not be used with the generic tuple type G_VARIANT_TYPE_TUPLE.
In the case of a dictionary entry type, this function will always return 2.
| VariantType & Glib::VariantType::operator= | ( | const GVariantType * | castitem | ) |
| VariantType & Glib::VariantType::operator= | ( | const VariantType & | src | ) |
|
noexcept |
|
noexcept |
| VariantType Glib::VariantType::value | ( | ) | const |
Determines the value type of a dictionary entry type.
This function may only be used with a dictionary entry type.
|
related |
| lhs | The left-hand side |
| rhs | The right-hand side |
|
related |
A Glib::wrap() method for this object.
| object | The C instance. |
| take_copy | False if the result should take ownership of the C instance. True if it should take a new copy or ref. |
|
protected |
1.9.4