GObject.ObjectClass

Fields

Name Type Access Description
construct_properties [object] r  
constructed object r  
constructor object r  
dispatch_properties_changed object r  
dispose object r  
finalize object r  
flags int r  
g_type_class GObject.TypeClass r the parent class
get_property object r  
notify object r  
pdummy [object] r  
set_property object r  

Methods

  find_property (property_name)
  install_properties (pspecs)
  install_property (property_id, pspec)
  list_properties ()
  override_property (property_id, name)

Details

class GObject.ObjectClass

The class structure for the GObject.Object 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;
}
find_property(property_name)[source]
Parameters:property_name (str) – the name of the property to look up
Returns:the GObject.ParamSpec for the property, or None if the class doesn’t have a property of that name
Return type:GObject.ParamSpec

Looks up the GObject.ParamSpec for a property of a class.

install_properties(pspecs)[source]
Parameters:pspecs ([GObject.ParamSpec]) – the GObject.ParamSpecs array defining the new properties

Installs new properties from an array of GObject.ParamSpecs.

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 GObject.ParamSpec in the pspecs array.

The property id of 0 is treated specially by GObject.Object and it should not be used to store a GObject.ParamSpec.

This function should be used if you plan to use a static array of GObject.ParamSpecs and GObject.Object.notify_by_pspec(). For instance, this class initialization:

enum {
  PROP_0, PROP_FOO, PROP_BAR, N_PROPERTIES
};

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", "Foo", "Foo",
                      -1, G_MAXINT,
                      0,
                      G_PARAM_READWRITE);

  obj_properties[PROP_BAR] =
    g_param_spec_string ("bar", "Bar", "Bar",
                         NULL,
                         G_PARAM_READWRITE);

  gobject_class->set_property = my_object_set_property;
  gobject_class->get_property = my_object_get_property;
  g_object_class_install_properties (gobject_class,
                                     N_PROPERTIES,
                                     obj_properties);
}

allows calling GObject.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]);
    }
 }

New in version 2.26.

install_property(property_id, pspec)[source]
Parameters:

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.

list_properties()[source]
Returns:an array of GObject.ParamSpec which should be freed after use
Return type:[GObject.ParamSpec]

Get an array of GObject.ParamSpec for all properties of a class.

override_property(property_id, name)[source]
Parameters:
  • property_id (int) – the new property ID
  • name (str) – the name of a property registered in a parent class or in an interface of this class.

Registers property_id as referring to a property with the name name in a parent class or in an interface implemented by self. 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 GObject.ParamSpecOverride; generally operations that query the properties of the object class, such as GObject.ObjectClass.find_property() or GObject.ObjectClass.list_properties() will return the overridden property. However, in one case, the construct_properties argument of the constructor virtual function, the GObject.ParamSpecOverride is passed instead, so that the param_id field of the GObject.ParamSpec will be correct. For virtually all uses, this makes no difference. If you need to get the overridden property, you can call GObject.ParamSpec.get_redirect_target().

New in version 2.4.