Getting Started with Flutter: A Beginner's Guide to Cross-Platform App Development

📘 Chapter 2: Understanding Dart — The Language Behind Flutter

🧭 What You’ll Learn

In this chapter, you’ll explore the Dart programming language, which powers Flutter development. You’ll learn:

• Why Dart is the language used by Flutter
• Core Dart syntax: variables, data types, functions, control flow
• Working with classes, objects, and constructors
• Null safety and type system
• Collections like lists, sets, and maps
• Asynchronous programming with Future and async/await
• Common Dart idioms in Flutter apps

💡 Why Dart?

Flutter apps are written in Dart because:

• Dart is fast and compiled to native ARM code
• It supports hot reload, essential for UI development
• Dart syntax is clean and modern—great for both beginners and pros
• It compiles to JavaScript, enabling web support for Flutter

🧱 Dart Basics

✅ Hello World in Dart

dart

void main() {

  print('Hello, Dart!');

}

You can run this in a Dart file or inside DartPad.

📌 Variables and Types

Dart is optionally typed, meaning you can use var, final, or explicitly specify types.

dart

var name = 'Flutter';

int age = 2;

double price = 19.99;

bool isAvailable = true;

Constant vs Final

dart

final currentYear = 2024; // Set once at runtime

const pi = 3.14159;       // Compile-time constant

🧠 Type Table

🔁 Control Flow

✅ If-Else

dart

int score = 85;

if (score >= 90) {

  print('A');

} else if (score >= 80) {

  print('B');

} else {

  print('C');

}

✅ Loops

dart

for (var i = 0; i < 5; i++) {

  print('i = $i');

}

while (score > 0) {

  score -= 10;

  print('Score: $score');

}

🧩 Functions in Dart

dart

int add(int a, int b) {

  return a + b;

}

// Arrow syntax

String greet(String name) => 'Hello, $name';

void main() {

  print(add(3, 4));            // 7

  print(greet('Flutter'));     // Hello, Flutter

}

🔷 Null Safety

Introduced in Dart 2.12, null safety ensures variables can’t be null unless specified.

dart

String? name = null; // Nullable

String username = 'guest'; // Non-nullable

// Null-aware operator

print(name ?? 'default'); // prints 'default'

✅ Null-Aware Operators

🧱 Object-Oriented Dart

✅ Classes and Constructors

dart

class User {

  String name;

  int age;

  // Constructor

  User(this.name, this.age);

  void greet() {

    print('Hi, I\'m $name and I\'m $age');

  }

}

void main() {

  var user = User('Alex', 30);

  user.greet(); // Hi, I'm Alex and I'm 30

}

🔁 Named and Optional Parameters

dart

class Product {

  String name;

  double price;

  Product({required this.name, this.price = 0.0});

}

var p = Product(name: 'Phone');

print(p.price); // 0.0

🧠 Dart Object Syntax Summary

🔢 Collections in Dart

✅ Lists

dart

var colors = ['red', 'green', 'blue'];

colors.add('yellow');

print(colors.length); // 4

✅ Sets (no duplicates)

dart

var uniqueNumbers = {1, 2, 3};

uniqueNumbers.add(2); // ignored

✅ Maps (key-value pairs)

dart

var user = {

  'name': 'John',

  'age': 28

};

print(user['name']); // John

🧠 List Operations Table

🔄 Async Programming with Futures

✅ Future Basics

dart

Future<String> fetchData() async {

  await Future.delayed(Duration(seconds: 2));

  return 'Data loaded!';

}

void main() async {

  print(await fetchData());

}

✅ Error Handling

dart

try {

  var data = await fetchData();

  print(data);

} catch (e) {

  print('Error: $e');

}

🔄 Stream Basics

Use streams when you expect multiple asynchronous values over time (e.g., live data or countdowns).

dart

Stream<int> counter() async* {

  for (int i = 0; i < 5; i++) {

    await Future.delayed(Duration(seconds: 1));

    yield i;

  }

}

🧠 Dart vs JavaScript Syntax Comparison

✅ Summary

You’ve now learned the fundamentals of Dart, including:

• Declaring variables, functions, and classes
• Using control structures and collections
• Working with null safety and optional parameters
• Performing asynchronous tasks with Future and Stream
• Applying OOP principles to structure your Flutter apps

With Dart as your tool, you’re ready to start building beautiful UIs in Flutter!