What are async and await in Dart?

In Dart, async and await are keywords used to handle asynchronous operations, which are tasks that take time to complete, like fetching data from a server, reading a file, or querying a database. They allow your program to wait for a task to complete without blocking the rest of the code, making it more efficient and responsive.

1. async:
   You mark a function as async when it performs asynchronous operations. This tells Dart that the function will return a Future, which represents a value that will be available later.

Future fetchData() async {
  // Simulate network delay
  await Future.delayed(Duration(seconds: 2));
  return "Data loaded";
}

await:
Inside an async function, you use await before a Future to pause execution until the Future completes. This makes asynchronous code easier to read, almost like synchronous code.

void main() async {
  print("Fetching data...");
  String data = await fetchData();
  print(data); // Output after 2 seconds: Data loaded
}

3. Practical Example:
   I’ve used async and await when building apps that fetch user profiles from APIs. Instead of blocking the UI while waiting for a network call, the app remains responsive, showing loading indicators until the data is ready.
4. Challenges:

• Forgetting to use await can cause code to execute before the asynchronous task completes.
• Exception handling requires care; you should use try-catch blocks to handle errors in async functions.

try {
  String data = await fetchData();
} catch (e) {
  print("Error occurred: $e");
}

Alternative:
Before async/await, Dart used then() with Futures:

fetchData().then((data) {
  print(data);
});

While this works, async/await makes the code much cleaner and easier to maintain, especially for multiple sequential asynchronous operations.