Classes (object orientation)

This lesson covers the basics of writing a class in Dart.

A class bundles data (fields) together with behaviour (methods). Dart is designed around the idea that everything is an object.

The sample code defines class Animal with a name field and a speak() method that returns the sound it makes.

A common early stumble is when fields get initialised. In Dart, a field not initialised in the constructor must either be marked with ? or be given an initial value, under the null-safety rules.

In professional work, almost every screen component (widget) in Flutter is defined as a class, so understanding classes is the foundation of Flutter development.

📖 Reference code

class Animal {
  String name;
  Animal(this.name);
  String speak() {
    return '$name is making a sound.';
  }
}

void main() {
  var dog = Animal('Rex');
  print(dog.speak());
}

✍️ Your code

Type your code, then press "Run"

🧪 This site can't compile or run Dart directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser — nothing is sent anywhere).