Async* in Dart

Dart is a modern, flexible programming language that is widely used for building web applications, mobile apps, and backend systems. One of its powerful features is the async* keyword, which allows you to define asynchronous generators.

What is an asynchronous generator?

An asynchronous generator is a function that returns an asynchronous sequence of values. You can think of it as a stream of data that is being generated over time. The async* keyword is used to define an asynchronous generator function.

Here is an example of an asynchronous generator that generates a sequence of numbers:

Stream<int> countToThree() async* {
  yield 1;
  yield 2;
  yield 3;
}

In this example, the async* keyword is used to define a function that returns a Stream<int>. The yield keyword is used to emit values from the function. When you call this function, it will return a stream that emits the numbers 1, 2, and 3.

Using async* with streams

Async generators are often used in conjunction with streams. You can use an asynchronous generator to produce a stream of data, and then use the stream to consume the data.

Here is an example of using an asynchronous generator to generate a stream of random numbers:

import 'dart:math';

Stream<int> randomNumbers(int count) async* {
  var random = Random();
  for (var i = 0; i < count; i++) {
    yield random.nextInt(100);
  }
}

void main() {
  // Generate a stream of 10 random numbers
  randomNumbers(10).listen((number) {
    print(number);
  });
}

In this example, the randomNumbers function is an asynchronous generator that generates a stream of random numbers. We use the listen method to subscribe to the stream and print each number.

Conclusion

Async generators are a powerful feature of Dart that allow you to create asynchronous sequences of data. You can use them to generate streams of data that can be consumed by other parts of your program. With async generators, you can write asynchronous code that is easier to read and maintain.