Dart Fundamentals

Dart is an object-oriented, class-based, garbage-collected language with C-style syntax. It can compile to either native code or JavaScript.

1. Null Safety

Dart’s Null Safety prevents null reference exceptions, a common cause of app crashes.

String? name;  // Nullable type. Can be null or text.
String name2;  // Non-nullable type. Must have a value.

[!TIP] Always use non-nullable types by default. Only use ? when a variable actually needs to be null.

Handling Null

use ?? to provide a fallback value.

print(name ?? 'Guest'); // Prints 'Guest' if name is null

2. Variables & Types

Dart supports type inference.

var name = 'Voyager I';
var year = 1977;
var antennaDiameter = 3.7;
var flybyObjects = ['Jupiter', 'Saturn', 'Uranus', 'Neptune'];

For constants, use final or const:

final: Value determined at runtime (once assigned, cannot change).
const: Value determined at compile-time.

final now = DateTime.now(); // Runtime constant
const pi = 3.14;            // Compile-time constant

3. Functions (Arrow Syntax)

For functions that contain just one expression, you can use a shorthand syntax:

bool isNoble(int atomicNumber) => _nobleGases[atomicNumber] != null;

4. Asynchronous Programming

Dart uses Future and Stream objects for asynchronous operations.

Async / Await

This is the modern way to write asynchronous code that looks synchronous.

Future<void> logIn() async {
  try {
    var user = await fetchUserFromApi();
    print('Logged in as ${user.name}');
  } catch (e) {
    print('Login failed: $e');
  }
}

5. Classes & Mixins

Dart is a single-inheritance language but supports Mixins to reuse code across multiple class hierarchies.

mixin Musical {
  void playInstrument(String instrumentName) {
    print('Plays the $instrumentName');
  }
}

class Musician extends Person with Musical {
  // ...
}

This is crucial for Flutter as the framework heavily relies on composition.