---
title: SignalBuilder
description: Learn how to use the SignalBuilder widget
---

# SignalBuilder

A signals widget builder.

Reacts to any number of *signals* calling the `builder` each time.

The `builder` argument must not be null.

The `child` is optional but is good practice to use if part of the widget
subtree does not depend on the value of the *signals*.

```dart
// sample counter
final counter = Signal(0);

@override
Widget build(BuildContext context) {
  return SignalBuilder(
        builder: (context, child) {
          return Text('${counter.value}');
        },
    );
}
```