Registers a private structure for an instantiatable type.
When an object is allocated, the private structures for the type and all of its parent types are allocated sequentially in the same memory block as the public structures, and are zero-filled.
Note that the accumulated size of the private structures of a type and all its parent types cannot exceed 64 KiB.
This function should be called in the type's class_init() function.
The private structure can be retrieved using the
G_TYPE_INSTANCE_GET_PRIVATE() macro.
The following example shows attaching a private structure
MyObjectPrivate to an object MyObject defined in the standard
GObject fashion in the type's class_init() function.
Note the use of a structure member "priv" to avoid the overhead of repeatedly calling MY_OBJECT_GET_PRIVATE().
typedef struct _MyObject MyObject;
typedef struct _MyObjectPrivate MyObjectPrivate;
struct _MyObject {
GObject parent;
MyObjectPrivate *priv;
};
struct _MyObjectPrivate {
int some_field;
};
static void
my_object_class_init (MyObjectClass *klass)
{
g_type_class_add_private (klass, sizeof (MyObjectPrivate));
}
static void
my_object_init (MyObject *my_object)
{
my_object->priv = G_TYPE_INSTANCE_GET_PRIVATE (my_object,
MY_TYPE_OBJECT,
MyObjectPrivate);
// my_object->priv->some_field will be automatically initialised to 0
}
static int
my_object_get_some_field (MyObject *my_object)
{
MyObjectPrivate *priv;
g_return_val_if_fail (MY_IS_OBJECT (my_object), 0);
priv = my_object->priv;
return priv->some_field;
}
size of private structure
Retrieves the class structure of the immediate parent type of the class passed in.
This is a convenience function often needed in class initializers.
Since derived classes hold a reference on their parent classes as long as they are instantiated, the returned class will always exist.
This function is essentially equivalent to: g_type_class_peek (g_type_parent (G_TYPE_FROM_CLASS (g_class)))
the parent class of g_class
Decrements the reference count of the class structure being passed in.
Once the last reference count of a class has been released, classes
may be finalized by the type system, so further dereferencing of a
class pointer after g_type_class_unref() are invalid.
Staticadjust_StaticgetStaticpeekRetrieves the class for a give type.
This function is essentially the same as g_type_class_get(),
except that the class may have not been instantiated yet.
As a consequence, this function may return null if the class
of the type passed in does not currently exist (hasn't been
referenced before).
type ID of a classed type
Staticpeek_Staticref
An opaque structure used as the base of all classes.