ListModel

class ListModel(*args, **kwargs)

Implementations: ListStore

GListModel is an interface that represents a mutable list of 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 notify signal). Taken together with the 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. 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: get_n_items returns the number of items in the list and 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 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 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 get_item_type and get_n_items respectively and be defined as such:

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);

Methods

class ListModel

get_item(position: int) → Object | 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.

Signals

class ListModel.signals

items_changed(position: int, removed: int, added: int) → None

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.

Added in version 2.44.

Parameters:

position – the position at which list changed
removed – the number of items removed
added – the number of items added

Virtual Methods

class ListModel

do_get_item(position: int) → Object | 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 get_n_items().

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

Added in version 2.44.

Parameters:: position – the position of the item to fetch

do_get_item_type() → type

Gets the type of the items in list.

All items returned from 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 ListModel can not change during the life of the model.

Added in version 2.44.

do_get_n_items() → 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 get_item() returns None.

Added in version 2.44.