---
title: Signals
description: Introduction to Signals
---

# Signals

Signals are the cornerstone of reactivity in `solidart`. They contain values that change over time; when you change a signal's value, it automatically updates anything that uses it.

Let's see how to create a Signal:
<Tabs
  groupId="library"
  values={[
    { label: 'Flutter', value: 'flutter' },
    { label: 'Dart', value: 'dart' },
  ]}
>
 <TabItem value="flutter">
    Import the `flutter_solidart` package:
    ```dart
    import 'package:flutter_solidart/flutter_solidart.dart';
    ```
  </TabItem>
  <TabItem value="dart">
    Import the `solidart` package:

    ```dart
    import 'package:solidart/solidart.dart';
    ```
  </TabItem>
</Tabs>

Next create the signal with:

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

The argument passed to the create call is the initial value, and the return value is the signal.

To retrieve the current value, you can use:
```dart
print(counter.value); // prints 0
// or
print(counter());
```

To change the value, you can use:
```dart
// Increments by 1
counter.value++; 
// Set the value to 2
counter.value = 2;
// equivalent to
counter.set(2);
// Update the value based on the current value
counter.updateValue((value) => value * 2);
```