---
title: SignalBuilder API docs
description: All the API docs of SignalBuilder
---

# SignalBuilder API docs

Reacts to the __signal__ calling the __builder__ each time.

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

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

## Constructor

```dart
SignalBuilder({
  required ValueWidgetBuilder<T> builder,
  Widget? child,
});
```
`builder` is the function that builds the widget and automatically reacts to any signal value changes.

`child` is optional and can be null if the entire widget subtree the __builder__ builds depends on the value of the __signals__. This widget will be passed to the `builder` and __DOESN'T__ rebuilds if the value of the __signals__ changes.

<Info>See also __DualSignalBuilder__and __TripleSignalBuilder__ to react to multiple signals</Info>