Functions
G_VALUE_HOLDS()
#define G_VALUE_HOLDS(value,type) (G_TYPE_CHECK_VALUE_TYPE ((value), (type)))
Checks if value
holds (or contains) a value of type
.
This macro will also check for value
!= NULL and issue a
warning if the check fails.
Returns
TRUE if value
holds the type
.
G_VALUE_TYPE()
#define G_VALUE_TYPE(value) (((GValue*) (value))->g_type)
Get the type identifier of value
.
G_VALUE_TYPE_NAME()
#define G_VALUE_TYPE_NAME(value) (g_type_name (G_VALUE_TYPE (value)))
Gets the type name of value
.
G_TYPE_IS_VALUE()
#define G_TYPE_IS_VALUE(type) (g_type_check_is_value_type (type))
Checks whether the passed in type ID can be used for g_value_init().
That is, this macro checks whether this type provides an implementation
of the GTypeValueTable functions required for a type to create a GValue of.
Returns
Whether type
is suitable as a GValue type.
G_TYPE_IS_VALUE_ABSTRACT()
#define G_TYPE_IS_VALUE_ABSTRACT(type) (g_type_test_flags ((type), G_TYPE_FLAG_VALUE_ABSTRACT))
Checks if type
is an abstract value type. An abstract value type introduces
a value table, but can't be used for g_value_init() and is normally used as
an abstract base type for derived value types.
G_IS_VALUE()
#define G_IS_VALUE(value) (G_TYPE_CHECK_VALUE (value))
Checks if value
is a valid and initialized GValue structure.
g_value_init ()
GValue *
g_value_init (GValue *value,
GType g_type);
Initializes value
with the default value of type
.
Returns
the GValue structure that has been passed in.
[transfer none]
g_value_copy ()
void
g_value_copy (const GValue *src_value,
GValue *dest_value);
Copies the value of src_value
into dest_value
.
g_value_reset ()
GValue *
g_value_reset (GValue *value);
Clears the current value in value
and resets it to the default value
(as if the value had just been initialized).
Returns
the GValue structure that has been passed in
g_value_unset ()
void
g_value_unset (GValue *value);
Clears the current value in value
(if any) and "unsets" the type,
this releases all resources associated with this GValue. An unset
value is the same as an uninitialized (zero-filled) GValue
structure.
g_value_init_from_instance ()
void
g_value_init_from_instance (GValue *value,
gpointer instance);
Initializes and sets value
from an instantiatable type via the
value_table's collect_value() function.
Note: The value
will be initialised with the exact type of
instance
. If you wish to set the value
's type to a different GType
(such as a parent class GType), you need to manually call
g_value_init() and g_value_set_instance().
Since: 2.42
g_value_set_instance ()
void
g_value_set_instance (GValue *value,
gpointer instance);
Sets value
from an instantiatable type via the
value_table's collect_value() function.
g_value_fits_pointer ()
gboolean
g_value_fits_pointer (const GValue *value);
Determines if value
will fit inside the size of a pointer value.
This is an internal function introduced mainly for C marshallers.
Returns
TRUE if value
will fit inside a pointer value.
g_value_peek_pointer ()
gpointer
g_value_peek_pointer (const GValue *value);
Returns the value contents as pointer. This function asserts that
g_value_fits_pointer() returned TRUE for the passed in value.
This is an internal function introduced mainly for C marshallers.
Returns
the value contents as pointer.
[transfer none]
g_value_type_compatible ()
gboolean
g_value_type_compatible (GType src_type,
GType dest_type);
Returns whether a GValue of type src_type
can be copied into
a GValue of type dest_type
.
Returns
TRUE if g_value_copy() is possible with src_type
and dest_type
.
g_value_type_transformable ()
gboolean
g_value_type_transformable (GType src_type,
GType dest_type);
Check whether g_value_transform() is able to transform values
of type src_type
into values of type dest_type
. Note that for
the types to be transformable, they must be compatible or a
transformation function must be registered.
Returns
TRUE if the transformation is possible, FALSE otherwise.
g_value_transform ()
gboolean
g_value_transform (const GValue *src_value,
GValue *dest_value);
Tries to cast the contents of src_value
into a type appropriate
to store in dest_value
, e.g. to transform a G_TYPE_INT value
into a G_TYPE_FLOAT value. Performing transformations between
value types might incur precision lossage. Especially
transformations into strings might reveal seemingly arbitrary
results and shouldn't be relied upon for production code (such
as rcfile value or object property serialization).
Returns
Whether a transformation rule was found and could be applied.
Upon failing transformations, dest_value
is left untouched.
GValueTransform ()
void
(*GValueTransform) (const GValue *src_value,
GValue *dest_value);
The type of value transformation functions which can be registered with
g_value_register_transform_func().
dest_value
will be initialized to the correct destination type.
g_value_register_transform_func ()
void
g_value_register_transform_func (GType src_type,
GType dest_type,
GValueTransform transform_func);
Registers a value transformation function for use in g_value_transform().
A previously registered transformation function for src_type
and dest_type
will be replaced.
[skip]
g_strdup_value_contents ()
gchar *
g_strdup_value_contents (const GValue *value);
Return a newly allocated string, which describes the contents of a
GValue. The main purpose of this function is to describe GValue
contents for debugging output, the way in which the contents are
described may change between different GLib versions.
Returns
Newly allocated string.
Types and Values
G_VALUE_INIT
#define G_VALUE_INIT { 0, { { 0 } } }
A GValue must be initialized before it can be used. This macro can
be used as initializer instead of an explicit { 0 } when declaring
a variable, but it cannot be assigned to a variable.
Since: 2.30
GValue
typedef struct {
} GValue;
An opaque structure used to hold different types of values.
The data within the structure has protected scope: it is accessible only
to functions within a GTypeValueTable structure, or implementations of
the g_value_*() API. That is, code portions which implement new fundamental
types.
GValue users cannot make any assumptions about how data is stored
within the 2 element data
union, and the g_type
member should
only be accessed through the G_VALUE_TYPE() macro.
G_TYPE_VALUE
#define G_TYPE_VALUE (g_value_get_type ())
The type ID of the "GValue" type which is a boxed type,
used to pass around pointers to GValues.
G_TYPE_VALUE_ARRAY
#define G_TYPE_VALUE_ARRAY (g_value_array_get_type ()) GLIB_DEPRECATED_MACRO_IN_2_32_FOR(G_TYPE_ARRAY)
G_TYPE_VALUE_ARRAY has been deprecated since version 2.32 and should not be used in newly-written code.
Use GArray instead of GValueArray
The type ID of the "GValueArray" type which is a boxed type,
used to pass around pointers to GValueArrays.