Gio.ListModel

Implementations:

Gio.ListStore

Methods

	get_item (position)
	get_item_type ()
	get_n_items ()
	items_changed (position, removed, added)

Virtual Methods

	do_get_item (position)
	do_get_item_type ()
	do_get_n_items ()

Properties

None

Signals

Name	Short Description
items-changed	This signal is emitted whenever items were added to or removed from list.

Fields

None

Class Details

class Gio.ListModel

Bases:

GObject.GInterface

Structure:

Gio.ListModelInterface

GListModel is an interface that represents a mutable list of [class`GObject`.Object]. Its main intention is as a model for various widgets in user interfaces, such as list views, but it can also be used as a convenient method of returning lists of data, with support for updates.

Each object in the list may also report changes in itself via some mechanism (normally the [signal`GObject`.Object::notify] signal). Taken together with the [signal`Gio`.ListModel::items-changed] signal, this provides for a list that can change its membership, and in which the members can change their individual properties.

A good example would be the list of visible wireless network access points, where each access point can report dynamic properties such as signal strength.

It is important to note that the GListModel itself does not report changes to the individual items. It only reports changes to the list membership. If you want to observe changes to the objects themselves then you need to connect signals to the objects that you are interested in.

All items in a GListModel are of (or derived from) the same type. [method`Gio`.ListModel.get_item_type] returns that type. The type may be an interface, in which case all objects in the list must implement it.

The semantics are close to that of an array: [method`Gio`.ListModel.get_n_items] returns the number of items in the list and [method`Gio`.ListModel.get_item] returns an item at a (0-based) position. In order to allow implementations to calculate the list length lazily, you can also iterate over items: starting from 0, repeatedly call [method`Gio`.ListModel.get_item] until it returns NULL.

An implementation may create objects lazily, but must take care to return the same object for a given position until all references to it are gone.

On the other side, a consumer is expected only to hold references on objects that are currently ‘user visible’, in order to facilitate the maximum level of laziness in the implementation of the list and to reduce the required number of signal connections at a given time.

This interface is intended only to be used from a single thread. The thread in which it is appropriate to use it depends on the particular implementation, but typically it will be from the thread that owns the thread-default main context (see [method`GLib`.MainContext.push_thread_default]) in effect at the time that the model was created.

Over time, it has established itself as good practice for list model implementations to provide properties item-type and n-items to ease working with them. While it is not required, it is recommended that implementations provide these two properties. They should return the values of [method`Gio`.ListModel.get_item_type] and [method`Gio`.ListModel.get_n_items] respectively and be defined as such:

``c properties[PROP_ITEM_TYPE] =

g_param_spec_gtype (“item-type”, NULL, NULL, G_TYPE_OBJECT,

G_PARAM_CONSTRUCT_ONLY | G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS);

properties[PROP_N_ITEMS] =

g_param_spec_uint (“n-items”, NULL, NULL, 0, G_MAXUINT, 0,

G_PARAM_READABLE | G_PARAM_STATIC_STRINGS);

``

get_item(position)

Parameters:

position (int) – the position of the item to fetch

Returns:

the object at position.

Return type:

GObject.Object or None

Get the item at position.

If position is greater than the number of items in self, None is returned.

None is never returned for an index that is smaller than the length of the list.

This function is meant to be used by language bindings in place of Gio.ListModel.get_item().

See also: Gio.ListModel.get_n_items()

New in version 2.44.

get_item_type()

Returns:

the GObject.GType of the items contained in self.

Return type:

GObject.GType

Gets the type of the items in self.

All items returned from Gio.ListModel.get_item() are of the type returned by this function, or a subtype, or if the type is an interface, they are an implementation of that interface.

The item type of a Gio.ListModel can not change during the life of the model.

New in version 2.44.

get_n_items()

Returns:

the number of items in self.

Return type:

int

Gets the number of items in self.

Depending on the model implementation, calling this function may be less efficient than iterating the list with increasing values for position until Gio.ListModel.get_item() returns None.

New in version 2.44.

items_changed(position, removed, added)

Parameters:

• position (int) – the position at which self changed

• removed (int) – the number of items removed

• added (int) – the number of items added

Emits the Gio.ListModel ::items-changed signal on self.

This function should only be called by classes implementing Gio.ListModel. It has to be called after the internal representation of self has been updated, because handlers connected to this signal might query the new state of the list.

Implementations must only make changes to the model (as visible to its consumer) in places that will not cause problems for that consumer. For models that are driven directly by a write API (such as Gio.ListStore), changes can be reported in response to uses of that API. For models that represent remote data, changes should only be made from a fresh mainloop dispatch. It is particularly not permitted to make changes in response to a call to the Gio.ListModel consumer API.

Stated another way: in general, it is assumed that code making a series of accesses to the model via the API, without returning to the mainloop, and without calling other code, will continue to view the same contents of the model.

New in version 2.44.

do_get_item(position) virtual

Parameters:

position (int) – the position of the item to fetch

Returns:

the object at position.

Return type:

GObject.Object or None

Get the item at position. If position is greater than the number of items in list, None is returned.

None is never returned for an index that is smaller than the length of the list. See Gio.ListModel.get_n_items().

The same GObject.Object instance may not appear more than once in a Gio.ListModel.

New in version 2.44.

do_get_item_type() virtual

Returns:

the GObject.GType of the items contained in list.

Return type:

GObject.GType

Gets the type of the items in list.

All items returned from Gio.ListModel.get_item() are of the type returned by this function, or a subtype, or if the type is an interface, they are an implementation of that interface.

The item type of a Gio.ListModel can not change during the life of the model.

New in version 2.44.

do_get_n_items() virtual

Returns:

the number of items in list.

Return type:

int

Gets the number of items in list.

Depending on the model implementation, calling this function may be less efficient than iterating the list with increasing values for position until Gio.ListModel.get_item() returns None.

New in version 2.44.

Signal Details

Gio.ListModel.signals.items_changed(list_model, position, removed, added)

Signal Name:

items-changed

Flags:

RUN_LAST

Parameters:

• list_model (Gio.ListModel) – The object which received the signal

• position (int) – the position at which self changed

• removed (int) – the number of items removed

• added (int) – the number of items added

This signal is emitted whenever items were added to or removed from list. At position, removed items were removed and added items were added in their place.

Note: If removed != added, the positions of all later items in the model change.

New in version 2.44.