Author: saqibkhan

This example shows how to create and handle custom exceptions.

class InsufficientFundsException implements Exception {
  final String message;

  InsufficientFundsException(this.message);

  @override
  String toString() => 'InsufficientFundsException: $message';
}

class BankAccount {
  double balance;

  BankAccount(this.balance);

  void withdraw(double amount) {
if (amount > balance) {
  throw InsufficientFundsException('Cannot withdraw \$${amount.toStringAsFixed(2)} with balance of \$${balance.toStringAsFixed(2)}');
}
balance -= amount;
print('Withdrawn: \$${amount.toStringAsFixed(2)}. New balance: \$${balance.toStringAsFixed(2)}');
  }
}

void main() {
  var account = BankAccount(100);

  try {
account.withdraw(50);
account.withdraw(60);
  } catch (e) {
print(e);
  }
}

This example demonstrates the use of Futures and Streams for asynchronous programming.

import 'dart:async';

void main() {
  // Using a Future
  print('Fetching data...');
  fetchData().then((data) {
print('Data received: $data');
  });

  // Using a Stream
  var numberStream = generateNumbers();
  numberStream.listen((number) {
print('Received number: $number');
  });
}

Future<String> fetchData() async {
  await Future.delayed(Duration(seconds: 2));
  return 'Sample Data';
}

Stream<int> generateNumbers() async* {
  for (var i = 1; i <= 5; i++) {
await Future.delayed(Duration(seconds: 1));
yield i;
  }
}

This example illustrates how to use mixins to share behavior between classes.

mixin Logger {
  void log(String message) {
print('LOG: $message');
  }
}

class User with Logger {
  String name;

  User(this.name);

  void sayHello() {
log('User $name says hello!');
  }
}

class Admin with Logger {
  String adminName;

  Admin(this.adminName);

  void performAdminTask() {
log('Admin $adminName is performing an admin task.');
  }
}

void main() {
  var user = User('Alice');
  user.sayHello();

  var admin = Admin('Bob');
  admin.performAdminTask();
}

This example demonstrates how to read from and write to files in Dart.

import 'dart:io';

void main() async {
  // Writing to a file
  var file = File('example.txt');
  await file.writeAsString('Hello, Dart!\nThis is a file I/O example.\n');

  print('File written: ${file.path}');

  // Reading from the file
  String contents = await file.readAsString();
  print('File contents:\n$contents');

  // Appending to the file
  await file.writeAsString('Appending new content.\n', mode: FileMode.append);
  contents = await file.readAsString();
  print('Updated file contents:\n$contents');
}

This example shows how to manipulate collections and use higher-order functions.

void main() {
  List<int> numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

  // Filtering even numbers
  var evenNumbers = numbers.where((number) => number.isEven).toList();
  print('Even Numbers: $evenNumbers');

  // Squaring the numbers
  var squaredNumbers = numbers.map((number) => number * number).toList();
  print('Squared Numbers: $squaredNumbers');

  // Summing all numbers
  var sum = numbers.reduce((a, b) => a + b);
  print('Sum of Numbers: $sum');

  // Finding the maximum number
  var maxNumber = numbers.reduce((a, b) => a > b ? a : b);
  print('Maximum Number: $maxNumber');
}