Explain async, await in Flutter/Dart?

In Dart, async and await are used to handle asynchronous operations in a more readable and sequential manner. They are part of the async-await feature, which allows you to work with Futures and other asynchronous operations without using nested callbacks (also known as “callback hell”).

  1. async Keyword: The async keyword is used to mark a function as asynchronous. It allows the function to use await to wait for the completion of asynchronous operations without blocking the execution of the whole program. The function returns a Future implicitly, which represents the result of the asynchronous computation.

Example of an async function:

Future<void> fetchData() async {
  // Asynchronous operations, such as making an API call or performing I/O.
  1. await Keyword: The await keyword is used inside an async function to wait for the completion of an asynchronous operation, typically a Future. When the await keyword is used, it suspends the execution of the function until the awaited operation completes, and then it extracts the result or handles any errors that occurred during the operation.

Example of using await to fetch data from an API:

Future<void> fetchData() async {
  // Simulating an API call that returns a Future.
  Future<String> apiCall = Future.delayed(Duration(seconds: 2), () => 'Data from API');

  // Using await to wait for the Future to complete and get the result.
  String data = await apiCall;

  print('Data: $data');

In this example, fetchData() is an async function that simulates an API call using Future.delayed. The await keyword is used to wait for the result of the apiCall Future, which completes after 2 seconds. Once the Future completes, the data variable holds the result, and it is printed to the console.

Async and await are powerful tools for working with asynchronous operations in a more readable and sequential manner, making the code easier to understand and maintain compared to using nested callbacks. They are commonly used in Flutter for tasks such as making network requests, reading and writing to files, and performing other I/O operations that can take time to complete. Remember that when using await, the function containing it must be marked as async, and the return type should be Future or a type that extends Future, indicating that the function will produce a result asynchronously.

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