Async/Await trong Dart

Future<String> fetchData() async {
  await Future.delayed(Duration(seconds: 2));
  return "Data loaded";
}
 
void main() async {
  print("Loading...");
  var data = await fetchData();
  print(data);  // Data loaded (sau 2 giây)
}

Future<int> calculateSum() {
  return Future.delayed(
    Duration(seconds: 1),
    () => 10 + 20
  );
}
 
void main() async {
  var sum = await calculateSum();
  print(sum);  // 30 (sau 1 giây)
}

Future<String> greet() async {
  return "Hello";
}
 
// Tương đương với:
Future<String> greet() {
  return Future.value("Hello");
}

void loadData() async {
  print("Start loading");
  var data = await fetchData();  // Đợi kết quả
  print("Data: $data");
}

Future<String> fetchData() async {
  throw Exception("Network error");
}
 
void main() async {
  try {
    var data = await fetchData();
    print(data);
  } catch (e) {
    print("Error: $e");
  }
}

void loadSequential() async {
  var data1 = await fetchData1();  // Đợi
  var data2 = await fetchData2();  // Đợi
  print("$data1, $data2");
}

void loadParallel() async {
  var results = await Future.wait([
    fetchData1(),
    fetchData2(),
  ]);
  print(results);
}

fetchData()
  .then((data) => print("Success: $data"))
  .catchError((error) => print("Error: $error"));

import 'dart:convert';
import 'package:http/http.dart' as http;
 
Future<Map<String, dynamic>> fetchUser(int id) async {
  final response = await http.get(
    Uri.parse('https://api.example.com/users/$id')
  );
 
  if (response.statusCode == 200) {
    return jsonDecode(response.body);
  } else {
    throw Exception('Failed to load user');
  }
}
 
void main() async {
  try {
    var user = await fetchUser(1);
    print("User: ${user['name']}");
  } catch (e) {
    print("Error: $e");
  }
}