textual.signal

Signals are a simple pub-sub mechanism.

DOMNodes can subscribe to a signal, which will invoke a callback when the signal is published.

This is experimental for now, for internal use. It may be part of the public API in a future release.

Signal ¶

Signal(owner, name)

Bases: Generic[SignalT]

A signal that a widget may subscribe to, in order to invoke callbacks when an associated event occurs.

Parameters:

Name	Type	Description	Default
`owner`	`DOMNode`	The owner of this signal.	required
`name`	`str`	An identifier for debugging purposes.	required

owner: DOMNode | None

The owner of this Signal, or None if there is no owner.

publish(data)

Publish the signal (invoke subscribed callbacks).

Parameters:

Name	Type	Description	Default
`data`	`SignalT`	An argument to pass to the callbacks.	required

subscribe(node, callback, immediate=False)

Subscribe a node to this signal.

When the signal is published, the callback will be invoked.

Parameters:

Name	Type	Description	Default
`node`	`MessagePump`	Node to subscribe.	required
`callback`	`SignalCallbackType`	A callback function which takes a single argument and returns anything (return type ignored).	required
`immediate`	`bool`	Invoke the callback immediately on publish if `True`, otherwise post it to the DOM node to be called once existing messages have been processed.	`False`

Raises:

Type	Description
`SignalError`	Raised when subscribing a non-mounted widget.

unsubscribe(node)

Unsubscribe a node from this signal.

Parameters:

Name	Type	Description	Default
`node`	`MessagePump`	Node to unsubscribe,	required

Raised for Signal errors.