GObject.ObjectClass¶
record (struct)
The class structure for the GObject type.
// Example of implementing a singleton using a constructor.
static MySingleton *the_singleton = NULL;
static GObject*
my_singleton_constructor (GType type,
guint n_construct_params,
GObjectConstructParam *construct_params)
{
GObject *object;
if (!the_singleton)
{
object = G_OBJECT_CLASS (parent_class)->constructor (type,
n_construct_params,
construct_params);
the_singleton = MY_SINGLETON (object);
}
else
object = g_object_ref (G_OBJECT (the_singleton));
return object;
}
Methods¶
find_property¶
Looks up the ParamSpec for a property of a class.
Parameters:
property_name— the name of the property to look up
install_properties¶
Installs new properties from an array of GParamSpecs.
All properties should be installed during the class initializer. It is possible to install properties after that, but doing so is not recommend, and specifically, is not guaranteed to be thread-safe vs. use of properties on the same type on other threads.
The property id of each property is the index of each ParamSpec in
the pspecs array.
The property id of 0 is treated specially by Object and it should not
be used to store a ParamSpec.
This function should be used if you plan to use a static array of
GParamSpecs and Object.notify_by_pspec. For instance, this
class initialization:
typedef enum {
PROP_FOO = 1,
PROP_BAR,
N_PROPERTIES
} MyObjectProperty;
static GParamSpec *obj_properties[N_PROPERTIES] = { NULL, };
static void
my_object_class_init (MyObjectClass *klass)
{
GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
obj_properties[PROP_FOO] =
g_param_spec_int ("foo", NULL, NULL,
-1, G_MAXINT,
0,
G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS);
obj_properties[PROP_BAR] =
g_param_spec_string ("bar", NULL, NULL,
NULL,
G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS);
gobject_class->set_property = my_object_set_property;
gobject_class->get_property = my_object_get_property;
g_object_class_install_properties (gobject_class,
G_N_ELEMENTS (obj_properties),
obj_properties);
}
allows calling Object.notify_by_pspec to notify of property changes:
void
my_object_set_foo (MyObject *self, gint foo)
{
if (self->foo != foo)
{
self->foo = foo;
g_object_notify_by_pspec (G_OBJECT (self), obj_properties[PROP_FOO]);
}
}
Parameters:
pspecs— theGParamSpecsarray defining the new properties
install_property¶
Installs a new property.
All properties should be installed during the class initializer. It is possible to install properties after that, but doing so is not recommend, and specifically, is not guaranteed to be thread-safe vs. use of properties on the same type on other threads.
Note that it is possible to redefine a property in a derived class, by installing a property with the same name. This can be useful at times, e.g. to change the range of allowed values or the default value.
Parameters:
property_id— the id for the new propertypspec— theParamSpecfor the new property
list_properties¶
Get an array of ParamSpec* for all properties of a class.
override_property¶
Registers property_id as referring to a property with the name
name in a parent class or in an interface implemented by oclass.
This allows this class to "override" a property implementation in
a parent class or to provide the implementation of a property from
an interface.
Internally, overriding is implemented by creating a property of type
ParamSpecOverride; generally operations that query the properties of
the object class, such as ObjectClass.find_property or
ObjectClass.list_properties will return the overridden
property. However, in one case, the construct_properties argument of
the constructor virtual function, the ParamSpecOverride is passed
instead, so that the param_id field of the ParamSpec will be
correct. For virtually all uses, this makes no difference. If you
need to get the overridden property, you can call
ParamSpec.get_redirect_target.
Parameters:
property_id— the new property IDname— the name of a property registered in a parent class or in an interface of this class.