Dart Future asStream()
Syntax & Examples

Future.asStream() method

The `asStream` method in Dart creates a Stream containing the result of a Future.

Syntax of Future.asStream()

The syntax of Future.asStream() method is:

 Stream<T> asStream()

This asStream() method of Future creates a Stream containing the result of this future.

Return Type

Future.asStream() returns value of type Stream<T>.


✐ Examples

1 Creating a stream from a Future

In this example,

  1. We create a Future called futureInt with a value of 42.
  2. We convert this future into a Stream using asStream().
  3. We listen to the stream and print received data.

Dart Program

void main() {
  Future<int> futureInt = Future.value(42);
  Stream<int> streamInt = futureInt.asStream();
  streamInt.listen((data) {
    print('Received data from stream: $data');
  });
}

Output

Received data from stream: 42

2 Creating a stream from a Future

In this example,

  1. We create a Future called futureString with the value 'Hello, Dart!'.
  2. We convert this future into a Stream using asStream().
  3. We listen to the stream and print received data.

Dart Program

void main() {
  Future<String> futureString = Future.value('Hello, Dart!');
  Stream<String> streamString = futureString.asStream();
  streamString.listen((data) {
    print('Received data from stream: $data');
  });
}

Output

Received data from stream: Hello, Dart!

3 Creating a stream from a Future>

In this example,

  1. We create a Future> called futureList with a list of integers [1, 2, 3, 4, 5].
  2. We convert this future into a Stream> using asStream().
  3. We listen to the stream and print received data.

Dart Program

void main() {
  Future<List<int>> futureList = Future.value([1, 2, 3, 4, 5]);
  Stream<List<int>> streamList = futureList.asStream();
  streamList.listen((data) {
    print('Received data from stream: $data');
  });
}

Output

Received data from stream: [1, 2, 3, 4, 5]

Summary

In this Dart tutorial, we learned about asStream() method of Future: the syntax and few working examples with output and detailed explanation for each example.