What is RxDart?

Rx is a popular pattern for reactive programming, and the RxDart package is a powerful library for implementing it in Flutter. In this article, we’ll explore the basics of using RxDart in a Flutter project, including how to set up streams, listen to events, and process data with operators.

Setting Up RxDart

To use RxDart in a Flutter project, add it to your dependencies in pubspec.yaml:

dependencies:
  rxdart: ^0.27.2

Then, run flutter pub get to install the package.

Creating a Stream

To start with RxDart, we need to create a Stream. A Stream is a sequence of events that can be listened to, and RxDart provides several ways to create them.

For example, we can create a simple stream that emits a sequence of integers using the Stream.fromIterable constructor:

final stream = Stream.fromIterable([1, 2, 3, 4, 5]);

Listening to a Stream

Once we have a Stream, we can listen to it and receive its events using the listen method:

stream.listen((event) {
  print(event);
});

This code will print the integers 1, 2, 3, 4, and 5 to the console.

Transforming a Stream

RxDart provides a variety of operators that allow us to transform, filter, and combine streams in powerful ways. Here’s an example that uses the map operator to transform a stream of integers into a stream of strings:

final stream = Stream.fromIterable([1, 2, 3, 4, 5]);

stream.map((event) => 'Value is $event').listen((event) {
  print(event);
});

This code will print the strings Value is 1, Value is 2, Value is 3, Value is 4, and Value is 5 to the console.

Filtering a Stream

We can also use the where operator to filter a stream based on a condition. Here's an example that only emits even integers:

final stream = Stream.fromIterable([1, 2, 3, 4, 5]);

stream.where((event) => event.isEven).listen((event) {
  print(event);
});

This code will print the integers 2 and 4 to the console.

Combining Streams

We can use the combineLatest operator to combine multiple streams into a single stream that emits events whenever any of the source streams emit an event. Here's an example that combines two streams of integers and sums their values:

final stream1 = Stream.fromIterable([1, 2, 3]);
final stream2 = Stream.fromIterable([4, 5, 6]);

Rx.combineLatest2(stream1, stream2, (a, b) => a + b).listen((event) {
  print(event);
});

This code will print the integers 5, 7, and 9 to the console.

Conclusion

In this article, we’ve explored the basics of using RxDart in a Flutter project, including creating streams, listening to events, and processing data with operators. RxDart is a powerful library that can help you build reactive and responsive user interfaces in Flutter, and it’s definitely worth exploring further.