Dart Future.wait()
Syntax & Examples

Future.wait() static-method

The `wait` static method in Dart waits for multiple futures to complete and collects their results.

Syntax of Future.wait()

The syntax of Future.wait() static-method is:

 Future<List<T>> wait<T>(Iterable<Future<T>> futures, { bool eagerError: false, void cleanUp(T successValue) })

This wait() static-method of Future waits for multiple futures to complete and collects their results.

Parameters

ParameterOptional/RequiredDescription
futuresrequiredAn iterable collection of futures.
eagerErroroptionalA boolean flag indicating whether to eagerly throw errors or wait for all futures to complete.
cleanUpoptionalA function to clean up resources after each future completes successfully.

Return Type

Future.wait() returns value of type Future<List<T>>.


✐ Examples

1 Waiting for integer futures

In this example,

  1. We create two delayed futures with different durations and integer values.
  2. We use Future.wait to wait for both futures to complete and collect their results.
  3. We print the collected results.

Dart Program

void main() async {
  Future<int> future1 = Future.delayed(Duration(seconds: 2), () => 42);
  Future<int> future2 = Future.delayed(Duration(seconds: 3), () => 84);
  List<int> results = await Future.wait([future1, future2]);
  print('Results: $results');
}

Output

Results: [42, 84]

2 Waiting for string futures

In this example,

  1. We create two delayed futures with different durations and string values.
  2. We use Future.wait to wait for both futures to complete and collect their results.
  3. We print the collected results.

Dart Program

void main() async {
  Future<String> future1 = Future.delayed(Duration(seconds: 3), () => 'Hello');
  Future<String> future2 = Future.delayed(Duration(seconds: 2), () => 'World');
  List<String> results = await Future.wait([future1, future2]);
  print('Results: $results');
}

Output

Results: [Hello, World]

Summary

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