# Signals

typed events, Connection handles, once-listeners and weak cleanup

```{raw} html
<a class="example-run-button" href="../demos/features_basics_signals.html">▶ Run in browser</a>


```

**Tags:** `basics` `signals` `events`

An Emitter node declares a typed `Signal(int)` class attribute. Each SPACE
press emits a tick to its listeners and every delivery is appended to an
on-screen log built from Text2D lines. One listener is connected with
`once=True` and spends itself on the first emit; the root listener can be
detached and re-attached live via its `Connection` handle; and an Echo node
holds a bound-method connection that cleans itself up when the node is freed.


## What it demonstrates

- `Signal(int)` as a class attribute: each instance lazily gets its own
  signal, so listeners on one emitter never hear another.
- `connect(fn)` returns a `Connection`; `conn.disconnect()` detaches it and
  `conn.connected` reports the state.
- `connect(fn, once=True)`: the listener auto-disconnects after one emit.
- Bound methods on Nodes are held weakly: freeing the node cleans the
  connection up and a later emit simply skips it, with no crash.

Controls:
  SPACE - emit ticked(n)
  D     - disconnect / reconnect the root listener via its Connection
  F     - free the Echo node (its bound-method connection auto-cleans)
  ESC   - quit

Run: uv run python examples/features/basics/signals.py
Headless self-check: uv run python examples/features/basics/signals.py --test

## Source

```{literalinclude} ../../examples/features/basics/signals.py
:language: python
:linenos:
```