Object Manager¶

The ObjectManager (binding for WpObjectManager) provides a way to collect a set of objects and be notified when objects that fulfill a certain set of criteria are created or destroyed.

To start an object manager, you first need to declare interest in a certain kind of object specifying a set of Interests in the constructor and then you need to activate it by calling ObjectManager.activate()

Upon activating an ObjectManager, any pre-existing objects that match the specified interests will immediately become available to get through ObjectManager.iterate() and the WpObjectManager “object-added” signal will be emitted for all of them.

Constructors¶

ObjectManager(interest_list)¶

Constructs a new object manager.

Combines wp_object_manager_new() and wp_object_manager_add_interest_full()

The argument needs to be a table that contains one or more Interest objects. The object manager will then contain all objects that match any one of the supplied interests.

Example:

streams_om = ObjectManager {
  -- match stream nodes
  Interest {
    type = "node",
    Constraint { "media.class", "matches", "Stream/*", type = "pw-global" },
  },
  -- and device nodes that are not associated with any routes
  Interest {
    type = "node",
    Constraint { "media.class", "matches", "Audio/*", type = "pw-global" },
    Constraint { "device.routes", "equals", "0", type = "pw" },
  },
  Interest {
    type = "node",
    Constraint { "media.class", "matches", "Audio/*", type = "pw-global" },
    Constraint { "device.routes", "is-absent", type = "pw" },
  },
}

The above example will create an ObjectManager that matches all nodes with a “media.class” global property that starts with the string “Stream/” and additionally all those whose “media.class” starts with “Audio/” and they have either a “device.routes” property that equals zero or they don’t have a “device.routes” property at all.

Parameters: interest_list (table) – a list of interests to objects
Returns: a new object manager
Return type: ObjectManager (WpObjectManager)

Methods¶

ObjectManager.activate(self)¶

Activates the object manager. Binds wp_core_install_object_manager().

Parameters: self – the object manager

ObjectManager.get_n_objects(self)¶

Binds wp_object_manager_get_n_objects()

Parameters: self – the object manager
Returns: the number of objects managed by the object manager
Return type: integer

ObjectManager.iterate(self, interest)¶

Binds wp_object_manager_new_filtered_iterator_full()

Parameters

self – the object manager
interest (Interest or nil or none) – an interest to filter objects

Returns

all the managed objects that match the interest

Return type

Iterator; the iteration items are of type GObject

ObjectManager.lookup(self, interest)¶

Binds wp_object_manager_lookup()

Parameters

self – the object manager
interest (Interest or nil or none) – the interest to use for the lookup

Returns

the first managed object that matches the interest

Return type

GObject