Dart Async

Await Keyword

The await keyword is used to execute async functions. It suspends the presently executing function and waits until the result of that async function is ready. It moves on to the next line of code once the result of the async function is returned. The await keyword is used only with async functions. For example,

// Asynchronous Function
asyncFunction() async {
  print("Inside async function");
}

// Main function to run the program
void main() async {
  // print statement before executing the async function
  print("Before Async Function");
  await asyncFunction(); // Executing the async function
  // print statement after executing the async function
  print("After Async Function");
}

Output:

Before Async Function
Inside async function
After Async Function

Future Keyword

Dart is a programming language with only one thread. The Future<T> object describes the outcome of an asynchronous operation that yields a result of type T. In case there is no useful value to be returned, the type of future is Future<void>. A Future asynchronously represents a single value, either data or an error. For example,

// Asynchronous Function
Future asyncFunction() async {
  final duration = Duration(seconds: 3);
  String message = "Inside async function";
  // It waits for 3 seconds before returning the answer
  return Future.delayed(duration).then((value) => message);
}

// Main function to run the program
void main() async {
  // print statement before executing the async function
  print("Before Async Function");
  await asyncFunction().then((result) {
    // It waits for the result and prints when the result is returned
    print(result);
  }); // Executing the async function
  // print statement after executing the async function
  print("After Async Function");
}

Output:

Before Async Function
Inside async function
After Async Function

Frequently Asked Questions

Why do we use the async modifier in the main function?

As the main function is executing an asynchronous function, it is mandatory to add the async modifier to the main function.

What are the most common methods to handle Futures?

Using the async and await keywords, as well as the Future API, are two of the most prevalent approaches for dealing with Futures.

How does the await keyword work?

Await effectively stops the control flow until the procedure is finished. To utilize await within a function, the function must be marked with the async keyword.

Conclusion 

In this article, we have extensively discussed the Async functions in Dart. We hope that this blog has helped you enhance your knowledge regarding the Dart Async, and to learn more, check out our other article on Dart Operators.
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