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.

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.

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 .

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).

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.

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.

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 .

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.

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).

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.

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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.

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.

1

GValue value = G_VALUE_INIT;

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 ())

The type ID of the "GValueArray" type which is a boxed type, used to pass around pointers to GValueArrays.